There seems to be no resolution to this, yet, right?
I have the exact same issue and apparently a few more as well as discussed in this thread: Android 10: no fingerprint for unlock
Except for me, as of yesterday, there is a new twist. Maybe that can help narrow down the root cause:
I always had the issue that the fingerprint stopped working for unlocking the phone after a random period. Although it is always working for other apps that require authentication like my banking app. Rebooting always fixed the issue. Until it happened again…
Now as of yesterday unlocking the phone with the fingerprint is not working at all anymore, not even after rebooting. Removing all fingerprints and re-adding one doesn’t solve the problem either. Except: I’ve done this procedure (i.e. a delete - add fingerprint cycle) now like 10 times and 2 times out of this I could unlock the phone for a few times. Before I couldn’t anymore because the sensor was just not reacting at the unlock screen. Again: all other apps can always use the sensor fine.
One maybe related information: I had an issue with my display yesterday. It was showing artifacts and generally failed to update properly. I realized this was likely a bad contact between screen and phone, so removed the screen, cleaned the contacts a little, and after that all was nice again. (Praises for the modular design!) Except now the fingerprint issue is as described above.
Any ideas what else I could try to triage the issue highly welcomed