Google Pixel 6 biometric unlock is not working

The checks in more detail

Clean the screen and your finger, because oil and moisture confuse the optical reader; dry or damp fingers fail more. A screen protector is the commonest cause: thick or air-gapped protectors block the reader, so use one made for under-display readers, or remove it to test. The first scan matters, so if the reader is unreliable, delete your prints and register them again in Settings, Security and privacy, Device unlock, Fingerprint, using different parts of the finger and registering the same finger twice. Settings can help too. Registering a finger on a screen protector you use, rather than the bare glass, gives the sensor the right data.

Update the phone, since Google has tuned the reader in software patches, and restart it. Cold hands, a cut on the finger and rough skin lower reliability, and you can add a second digit as a backup. If the fingerprint stops working after an update or a drop, boot into Safe mode and test, and then reset the fingerprints. If the reader does nothing on any finger with the protector off, the hardware may be at fault, and a screen replacement can disturb the reader, which needs a proper repair.

Keep a strong PIN as the fallback, never rely on the reader alone, and back up before any service. Be realistic about the hardware. The optical reader in the Pixel 6 reads the pattern by shining light through the screen, so a worn, scratched screen over the reader reduces accuracy, and a replacement display fitted by a third party may not match the factory calibration. If the phone has had a screen repair, ask the shop whether the reader was recalibrated. Google's software updates since launch have improved the reader, so owners who gave up on it early may find it better after the latest patch.