How to Fix Android Notifications Not Coming Through | LINE, Gmail, and App-Specific Checklist

Missing a LINE message or a Gmail alert can be more than an inconvenience — it can mean missing an important meeting reminder, a delivery update, or a message from a family member. Android has many settings that can silently block notifications, and they are spread across several different menus. The system-level notification toggle, Do Not Disturb schedules, battery optimization rules, data saver restrictions, and manufacturer-specific background app limits can all interfere independently, making the root cause hard to track down. This guide organizes every setting you need to check into a clear priority order, covers the most commonly affected apps — LINE, Gmail, and Slack — and includes brand-specific steps for Samsung Galaxy, Sony Xperia, OPPO, and Xiaomi devices where the defaults are often stricter than stock Android.

Table of Contents

1. Basic Notification Settings Check
   1. Checking System-Level Notification Permissions
   2. Checking In-App Notification Settings
   3. Checking Notification Channels
2. Silent Mode and Do Not Disturb
   1. Checking Silent Mode
   2. Checking Do Not Disturb Schedules
   3. Checking Focus Mode
3. Battery Optimization Exceptions
   1. How to Exempt an App from Battery Optimization
4. Data Saver and Power Saving Mode
   1. Checking Data Saver
   2. Checking Power Saving Mode
5. Auto-Start Restrictions
   1. What Auto-Start Restriction Does
   2. Allowing Auto-Start (General Steps)
   3. Allowing Background Activity
6. Device-Specific Settings (Galaxy, Xperia, OPPO, Xiaomi)
   1. Samsung Galaxy
   2. Sony Xperia
   3. OPPO / OnePlus / realme
   4. Xiaomi / Redmi / POCO
7. App-Specific Fixes (LINE, Gmail, Slack)
   1. LINE Notification Settings
   2. Gmail Notification Settings
   3. Slack Notification Settings
   4. Network Connectivity Check
   5. Updating Google Play Services
8. Frequently Asked Questions
9. Summary

Basic Notification Settings Check

When notifications stop arriving, start at the system level. Android notification settings have two layers: a system-wide permission per app, and within many apps a second layer of in-app controls. Both must be enabled for notifications to appear.

Checking System-Level Notification Permissions

1. Open Settings.
2. Tap Notifications or Apps and notifications.
3. Tap App notifications or See all apps.
4. Find the app that is not sending notifications.
5. Tap the app name and check whether Notifications is set to Off.
6. If it is off, toggle it on.

Checking In-App Notification Settings

Most apps have their own notification preferences inside the app itself, separate from the system setting. LINE, for example, has a detailed notification section under its own settings menu. The system permission could be on while the in-app setting is off, resulting in no notifications. Always check both layers.

Recommended check order:

1. System notification permission for the app
2. In-app notification settings
3. Silent mode and Do Not Disturb status
4. Battery optimization settings
5. Manufacturer-specific background restrictions

Checking Notification Channels

Since Android 8.0, apps can organize notifications into categories called channels. A messaging app might have separate channels for direct messages, group messages, and calls. If only certain types of notifications are missing, a specific channel may be disabled.

1. Go to Settings, then Apps, then tap the app with missing notifications.
2. Tap Notifications.
3. Review the list of notification categories shown under the app.
4. Check whether any category that should be active is toggled off.

Silent Mode and Do Not Disturb

Checking Silent Mode

Silent mode suppresses notification sounds and vibration. Depending on the device, banners and badge counts may still appear on screen, but you will not hear or feel any alert.

To check:

1. Press a volume button to bring up the volume panel.
2. Look at the icon next to the notification sound slider. A bell with a line through it means silent mode is active.
3. Tap the icon to cycle back to Sound on (a plain bell icon).

You can also check and toggle silent mode from the Quick Settings panel by swiping down from the top of the screen.

Checking Do Not Disturb Schedules

Do Not Disturb (DND) can be set to activate automatically on a schedule, which may explain why notifications disappear during certain hours even when you have not turned DND on manually.

1. Go to Settings, then Notifications, then Do Not Disturb or Quiet time.
2. Check whether DND is active.
3. Look for any automatic rules or schedules under Schedules or Auto rules and verify that none are running at an unexpected time.

From Quick Settings:

1. Swipe down from the top of the screen with two fingers to expand Quick Settings.
2. If the Do Not Disturb tile is highlighted, tap it to turn it off.

Checking Focus Mode

Devices running Android 10 or later include Focus Mode (found under Digital Wellbeing). When active, Focus Mode can block all notifications from selected apps.

1. Go to Settings, then Digital Wellbeing and parental controls.
2. Tap Focus Mode.
3. Check the list of apps marked as distracting. If the app you are troubleshooting appears there, remove it or turn Focus Mode off.

Battery Optimization Exceptions

Android's battery optimization feature limits background activity to extend battery life. When it applies strict restrictions to a messaging or email app, that app can no longer maintain its connection to the server in the background, so push notifications never arrive — or arrive very late.

How to Exempt an App from Battery Optimization

Standard Android (Pixel and similar):

1. Go to Settings, then Apps.
2. Tap the app that is not delivering notifications.
3. Tap Battery.
4. Select Unrestricted or No restrictions.

Android 12 and later:

1. Go to Settings, then Battery, then Battery usage.
2. Tap the app.
3. Under Background battery usage, select Unrestricted.

Reviewing all apps at once:

1. Go to Settings, then Battery, then Battery optimization (or App battery management).
2. Switch the dropdown from "Not optimized" to "All apps."
3. Find the app. If it is listed as Optimized, tap it and change the setting to Don't optimize.

Keep in mind that exempting an app from battery optimization allows it to run in the background freely, which increases battery consumption. Limit this to apps where timely notifications genuinely matter — such as LINE, Gmail, and calendar apps.

Data Saver and Power Saving Mode

Checking Data Saver

When Data Saver is active, apps that are not in the foreground cannot use mobile data, which prevents push notifications from being delivered over a cellular connection.

1. Go to Settings, then Network and Internet, then Data Saver.
2. If Data Saver is on, tap Unrestricted data or Exceptions and add the apps you want to receive notifications from.
3. Alternatively, turn Data Saver off entirely.

Checking Power Saving Mode

Power Saving Mode (or Battery Saver) restricts background activity across the entire device, which can delay or block notifications.

1. Go to Settings, then Battery, then Power saving mode or Battery saver.
2. If it is on, turn it off.
3. Check whether Power Saving Mode is set to turn on automatically at a certain battery level (for example, below 15%). Raising that threshold or disabling the automatic rule can prevent unexpected notification gaps.

From Quick Settings:

Swipe down from the top of the screen and look for a battery or power icon that is highlighted or labeled "Saving." Tap it to disable Power Saving Mode.

Auto-Start Restrictions

What Auto-Start Restriction Does

Some Android manufacturers — especially Xiaomi, OPPO, and Huawei — include a security feature that prevents apps from launching automatically at boot. When this restriction is active, the app cannot run in the background at all after the phone restarts, which means it cannot receive push notifications until you manually open it.

Allowing Auto-Start (General Steps)

1. Open Settings.
2. Go to Apps or App management.
3. Tap the app you want to fix.
4. Look for an Auto-start or Startup option under Battery or Other permissions.
5. Enable it.

The exact location of this setting varies by manufacturer. See the device-specific section below for detailed paths.

Allowing Background Activity

1. Open the app's detail page in Settings.
2. Tap Battery or Battery optimization.
3. Enable Allow background activity or set the option to No restrictions.

Device-Specific Settings (Galaxy, Xperia, OPPO, Xiaomi)

Samsung Galaxy

Samsung's Device Care system can place apps in a "sleeping" state to save battery, which stops them from receiving notifications.

Removing an app from the Sleeping Apps list:

1. Go to Settings, then Device Care (or Battery and device care), then Battery.
2. Tap Background usage limits.
3. Check the lists under Sleeping apps, Deep sleeping apps, and Never sleeping apps.
4. If the app you want to fix is in a sleeping category, tap it and remove it, or move it to Never sleeping.

Adaptive Battery:

1. Go to Settings, then Device Care, then Battery, then More battery settings.
2. Adaptive Battery learns your usage patterns and may throttle notifications for apps you open infrequently. If a notification-critical app is being throttled, consider turning Adaptive Battery off or adding the app to the Never sleeping list instead.

Turning off battery optimization per app:

1. Go to Settings, then Apps, then tap the app, then Battery.
2. Select Unrestricted.

Sony Xperia

Xperia's STAMINA mode restricts background activity to extend battery life, which can delay or block notifications.

Checking STAMINA mode:

1. Go to Settings, then Battery Care, then STAMINA mode.
2. If STAMINA mode is on, either turn it off or tap STAMINA mode exceptions and add the apps you want to receive notifications from.

Checking per-app background restrictions:

1. Go to Settings, then Battery Care, then Battery usage.
2. Under App background activity, check whether the affected app is listed as restricted.

OPPO / OnePlus / realme

These devices run ColorOS, which includes its own aggressive power management system.

Enabling auto-start:

1. Go to Settings, then Apps, then tap the app.
2. Tap Auto-start and enable it.

Removing from battery optimization:

1. Go to Settings, then Battery, then Battery optimization.
2. Find the app and set it to Not optimized (or Allow).

Note for OPPO users with App Cloner:

If you have cloned LINE or another messaging app using OPPO's App Cloner feature, you must also check and update the notification and auto-start settings for the cloned version separately from the original.

Xiaomi / Redmi / POCO

Xiaomi devices running MIUI have some of the strictest background management defaults of any Android variant. Missing notifications on Xiaomi phones are more common than on other brands, and typically require adjusting multiple settings.

Enabling auto-start:

1. Go to Settings, then Apps, then Manage apps.
2. Tap the app.
3. Enable Autostart.

Allowing unrestricted background activity:

1. Go to Settings, then Apps, then Manage apps.
2. Tap the app, then tap Battery saver.
3. Select No restrictions.

Checking other permissions:

1. Go to Settings, then Apps, then Manage apps.
2. Tap the app, then Other permissions.
3. Confirm that Display pop-up windows while running in the background is enabled.

App-Specific Fixes (LINE, Gmail, Slack)

LINE Notification Settings

LINE is one of the most frequently reported apps for missing notifications. In addition to Android system settings, LINE has its own internal notification configuration.

System settings for LINE:

1. Go to Settings, then Apps, then LINE, then Notifications.
2. Make sure Allow notifications is toggled on.
3. Review individual notification channels (Messages, Calls, etc.) and confirm none of them are disabled.

In-app settings for LINE:

1. Open LINE.
2. Tap More (the three-line icon at the bottom right).
3. Tap Settings, then Notifications.
4. Confirm that Message notifications is on.
5. Check that the notification sound is not set to None.
6. Look at the bottom of the Notifications screen for Pause notifications — make sure this is not active.

Chat-room-level settings:

If only one specific chat or group is not sending notifications, that room's notifications may be turned off individually.

1. Open the chat room with missing notifications.
2. Tap the menu icon in the upper right.
3. Tap Notifications and switch it on.

Gmail Notification Settings

System settings for Gmail:

1. Go to Settings, then Apps, then Gmail, then Notifications.
2. Confirm that notifications are allowed.

In-app settings for Gmail:

1. Open Gmail.
2. Tap the menu icon (three horizontal lines) in the upper left.
3. Tap Settings.
4. Tap the email account you want to configure.
5. Make sure Email notifications is enabled.
6. Choose a notification scope — All, High priority only, or the setting that fits your needs.

Sync settings:

1. Go to Settings, then Accounts, then Google.
2. Tap your account.
3. Tap Account sync and confirm that Gmail sync is enabled.

Slack Notification Settings

In-app settings for Slack:

1. Open Slack.
2. Tap your profile picture or the You tab.
3. Tap Notifications.
4. Under On mobile, confirm that notifications are set to Always or When I'm not active on desktop.
5. Check whether a notification schedule is active. A schedule limits notifications to certain hours of the day, which can cause missed alerts outside those hours.

Network Connectivity Check

Push notifications are delivered over an internet connection. If the connection is unstable or disconnected, no notifications will come through regardless of app settings.

1. Verify that Airplane mode is off.
2. Check that the Wi-Fi or mobile data icon appears in the status bar.
3. If you typically leave mobile data off, be aware that when your Wi-Fi drops, no backup connection is available and notifications will stop.

Updating Google Play Services

Google Play Services is the system component that handles push notification delivery (using Firebase Cloud Messaging). An outdated version can silently cause notification delivery failures.

1. Open the Google Play Store.
2. Tap your profile icon in the upper right.
3. Tap Manage apps and device, then Updates available.
4. If Google Play Services appears in the update list, tap Update.

For more Android troubleshooting tips, see Common Android Problems and How to Fix Them.

Frequently Asked Questions

Q. Notifications only stop coming during certain hours of the day. What is causing this?

A. A scheduled Do Not Disturb rule or a Focus Mode schedule is almost certainly the cause. Go to Settings, then Notifications, then Do Not Disturb, and review any automatic rules or schedules listed there. Also check Digital Wellbeing for active Focus Mode schedules.

Q. I get notifications in the background but not when the screen is on. Why?

A. The app's notification display behavior may be set to show banners only on the lock screen, or the banner (heads-up) setting may be turned off. Go to Settings, then Apps, tap the app, then Notifications. Look for a Behavior or Alert setting and confirm that on-screen banners are enabled.

Q. I reinstalled the app but notifications are still not coming through. Why?

A. Reinstalling the app resets its data but does not reset phone-level restrictions like battery optimization or auto-start settings. After reinstalling, go back through the battery optimization exemption steps and re-enable auto-start for the app — these settings are stored on the device, not inside the app.

Q. The app sends notifications but I hear no sound. What should I check?

A. Notification sound is configured per notification channel. Go to Settings, then Apps, tap the app, then Notifications, and open each channel. Confirm that a sound is assigned and that the channel's importance level is set to at least Default. Also check that the system notification volume (separate from media volume) is not set to zero.

Q. Notifications stopped working after an Android update. What should I do?

A. OS updates can reset battery optimization settings to their defaults, re-enabling optimization for apps that were previously exempted. After any major Android update, revisit the battery optimization section of this guide and re-exempt any apps that need to deliver time-sensitive notifications. Xiaomi and Samsung devices are particularly prone to this behavior after updates.

Summary

Android notification problems are caused by a layered set of controls — any one of them being set incorrectly is enough to block notifications entirely. The most efficient order to check them is: system notification permission, Do Not Disturb and Focus Mode, battery optimization, data saver, and then manufacturer-specific auto-start and background restrictions.

Xiaomi, OPPO, and Samsung Galaxy devices require extra steps beyond standard Android settings because their battery management systems are unusually aggressive by default. For apps like LINE and Gmail where missing a notification has real consequences, exempting them from battery optimization and enabling auto-start is worth doing proactively — even before you notice a problem.