This is according to a post on the Google Product Forums (via Android and Me) where some users are complaining about the issue. One user writes, “After updating I got the following message in red at the bottom of the screen when trying to unlock my phone with my fingerprint “Fingerprint hardware not available.” I tried rebooting and clearing my cache with no change. I thought if I deleted my fingerprints and re-added them it might help. Instead I just get the following error when trying to add a fingerprint: “Enrollment was not completed. Fingerprint enrollment didn’t work. Try again or use a different finger.””
The good news is based on the comments made by Orrin, the Pixel Community Manager, Google is aware of the problem and they are trying to gather as much information as possible in order to determine what might have caused the problem. So like we said, if you haven’t updated yet then maybe you want to hold off until the problem can be identified and resolved.
In the meantime it does not seem to be affecting other handsets, so for now it looks like it might be a Pixel and Nexus problem although we can’t say for sure how widespread it is yet.