There are many different vendors with slightly different implementations, which can make it difficult to determine why you're not receiving notifications on Android. However, the issue is usually caused by certain settings blocking notifications altogether. Try the following:
1. Settings > Notifications or Mode > Do Not Disturb:
If this setting is enabled, you won't receive push notifications. Make sure this is disabled.
2. Settings > Notifications > App Notifications
Check that the app in question has notifications enabled.
3. Settings > Apps > Your App > Notifications:
Make sure the Allow notifications toggle switch is turned on, and that are notifications are allowed on your Lock screen, as an App icon badge, and as a Notification pop-up.
4. Settings > Apps > App battery usage > Your App :
Make sure your app has Allow background usage turned on.
5. Settings > Battery > Power saving
Ensure Power saving is disabled.
6. Settings > Battery > Background usage limits
Check that the app in question isn't listed under Sleeping apps or Deep sleeping apps.
7. Settings > Apps > Chrome > Notifications:
Ensure that all toggle switches are turned on.
8. Settings > Battery > Battery usage > Chrome
Ensure Allow background usage is enabled.
