Face ID disabled

Have a look at these two articles -

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

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

If Face ID isn't working on your iPhone.

If Face ID isn't working on your iPhone or iPad Pro - Apple Support (AZ)

There is most likely a hardware issue with the phone. Make an appointment at the Genius Bar to have it diagnosed.

Genius Bar Reservation and Apple Support Options - Apple

Replace the parts with genuine ones, that is the only solution I can think of.