How can I clear this notification

Do a backup and try a factory reset. Then restore from your backup.

Restore to Factory setting.      

Backup - Restore your device from an iCloud or iTunes backup.      

For Face ID

Face ID on your iPhone or iPad Pro.   

Face ID - If an alert says has been disabled on your iPhone or iPad Pro

Face ID on your iPhone X - Get help with   

Face ID not working

Face ID not working' problems on iPhone

Fix iPhone X Face ID Not Working

Face ID Not Working

Marking your own post as Solved may prevent others from trying to help because they think you have fixed your problem.

What notification? More information would help.

How can I clear this notification