Some users may experience an issue with the fingerprint scanner (reader) not working properly on the lock screen of their Pixel 5, Pixel 4a or Pixel 3 phones.
Here are steps to fix Fingerprint sensor not working on Pixel phones:
Step 1: Clean the fingerprint reader with a soft cloth and a little water.
Step 2: Place adhesive transparent tape on it.
Step 3: Now head to Settings then Security then Pixel Imprint and remove registered fingerprint.
Step 4: Register the same finger multiple times with different angles.
After applying the above steps, your fingerprint reader should be working as usual.