Google has recently launched a new software update for the Android operating system. The new Android 7.1.2 is just an incremental update that is aimed at fixing some bugs and improving overall system stability, but unfortunately it does just the opposite for certain Pixel and Nexus smartphones.
Once you install the update, you won't be able to use fingerprint sensor on the Pixel, Pixel XL, Nexus 5X and Nexus 6P smartphones. There is currently no workaround available and the cause of the problem hasn't been identified yet. Google has yet to confirm the issue.