OPPO mobile phone automatically turns off the notification bright screen function.

Cute, according to your situation, we can try to just restore the system settings (all the system settings in the settings) and then restart the phone.

ColorOS 12 and later: enter Settings >; System settings > reset phone > restore system settings only.

Coloros11-1.3 version: Settings >; Other settings > restore phone > restore all settings only.

(Little European sauce tip: The information will not be cleared, but it will affect the system settings such as theme, ringtone and desktop layout. )