If you see a 'Screen overlay detected' error (see example image below), it's caused by conflict between a running app and a newly installed app requesting permission to display info on multiple screens (e.g., messengers, alerts, battery status, etc.).
From a Home screen, navigate: Apps > Settings.
If you're unable to access settings, first place your device into Safe Mode.
Tap the Search icon (located at the top), then enter over other apps into the search field.
Tap one of the following:
Draw over other apps
Display over other apps
Tap any app on the list to then tap one of the following to turn or off :
Allow display over other apps
Permit drawing over other apps
From a Home screen, relaunch the app.
If prompted, tap the available permissions (e.g., Permit Drawing over other apps, Contacts, etc.) to turn on or off.
Repeat steps (4-6) as needed to identify the app causing the error.