SumanBabu , via OnePlus Nord , Mar 3, 2021 : Notifications are not working when the app is closed. It is only working in minimize mode. OnePlus nord after getting the update this issue is showing.
Shailender Sharma , Mar 4, 2021 : Do the routine things, check the notifications permission in the Settings, clear the app cache, reset the app preferences and restart your device. If not resolved, submit your feedback here - https://forums.oneplus.com/feedback/
SumanBabu , via OnePlus Nord , Mar 4, 2021 : Done all but still this problem persists. May be it is a bug