1. Check the cable connector in your lock and make sure that there are no bent pins, which may have happened during installation, and that it is fully inserted into the socket.
2. If the pins are not bent, try a new fresh set of AA batteries.
3.  Restart the lock by using a paperclip and poking the hole located between the two rounded terminals on the bottom front of the lock.  Press and hold for 5 seconds and you should see the screen restart.

Your fingerprint sensor should work after a restart.

Note: Restart the lock, don’t reset the lock.