Finger print is not working

If you received a screen replacement from a non-apple-certified repair centre then they may have replaced the home button and therefore stopped you from ever being able to use Touch ID again. In this case I would recommend contacting the repairr store and asking them to fix the issue.

Greyed out meaning the function is unavailable at that moment. Try and go to “reset all settings” and try again if still its not working have your device checked on.