Have you been able to try and add the fingerprint while your phone is in safe mode? You can get your device into safe mode by following these steps:
-Hold power button until the 3 options of power off, restart, and emergency mode appear
-On-screen tap and hold on the power off option until it changes to safe mode
-Select safe mode and the phone will reboot into safe mode
-Once in safe mode try to re-add the fingerprint
Let me know if this helped!