After the Android 7.1.2 update, it seems that many users are experiencing problems with their fingerprint sensors. The sensor is no longer working to unlock the device or to register new fingerprints.
This problem is affecting the two Google Pixel phones as well as the Nexus 5X and Nexus 6P. The issue is likely not hardware, as the sensor still recognizes the swipe down for notifications gesture, so we’re hoping that Google can fix this with a software update and not resort to replacing devices.
Google has not responded to the issue so far, but there are forum threads documenting it. If you’re experiencing the same issue, hit the source link and post about it.