Android device cannot receive push notifications when an application is force stopped ("killed")

You may encounter some issues with notifications delivery due to Android modifications made by several device manufacturers. In most cases, these issues are caused by power-saving settings applied by default — apps are killed when they are not being used and don't start in the background when a notification is received.

Here are some workarounds to overcome these settings and receive notifications. 

Huawei 

Android 9 and later 

1. Go to Settings > Battery, and disable "Performance mode", "Power Saving mode", and "Ultra Power Saving mode". 
2. Go to Settings > Battery > App launch. 
3. Toggle the "Manage automatically" for the app to Off. Make sure to activate all three options of the Manage manually toggle: "Auto-launch", "Secondary launch", and "Run in background". 

Older EMUI versions: 

Depending on the device and OS version, the location of menu items may differ. 

1. Go to Settings > Battery > Find the app you'd like to receive notifications from and change the "Close apps after screen lock" to "Don't close".
2. Go to Settings > Apps > choose the app > Data usage, scroll down, and set "Background data" to "allowed". 

Sony 

STAMINA mode on Sony devices blocks apps in the background when the phone is in standby mode. STAMINA mode, available on some Sony Xperia devices, prevent apps from starting in the background and receiving notifications. 

To receive push notifications, set apps to be active in STAMINA mode:

1. Tap the Application screen icon on your home screen. 
2. Choose Settings > Power management, then select STAMINA mode. 
3. Turn on the Extended standby, then tap Apps active in standby > Add your applications. 
4. Scroll left or right to view all applications and services, then mark the relevant checkboxes for the apps you want to run. 
5. Tap Done. 

Asus

1. Go to Settings > Apps & Notifications > enable notifications for the app. 
2. Go to Auto-Start Manager > enable it for the app. 
3. Settings > Apps & Notifications > Special app access > enable for the app. 

Xiaomi

To fix MIUI push notifications, set the app to auto-start and disable battery optimization for that app: 

1. Go to Settings > Apps > Permissions > Autostart > choose the app and toggle the slider so that the app will always start in the background. 
2. Go to Settings > Battery & performance > Choose apps > select the app and choose No restrictions options.

Oppo 

1. Disable battery optimization 

Go to Settings > Battery > Battery optimization > choose the app and select "Do not optimize".

2. Disable energy saver 

Go to Settings > Battery > Energy saver > choose the app and turn off "Freeze when in Background" and "Automatically optimize when an anomaly is detected", then restart your phone. 

3. Set notifications as priority 

Go to Settings > Notifications & status bar > Notification Manager > select the app and turn on "Allow Notifications", "Display on Lockscreen", "Display at the top of the screen", "Notification Sound and Vibration", and "Priority notification". Then, restart your phone. 

4. Select Autostart for the app 

Go to System Organization > Security > Privacy permissions > Startup Manager > activate the Autostart for the app. 

Samsung 

Check the Samsung troubleshooting guide here: https://www.samsung.com/us/support/troubleshooting/TSG01001588/