Comment by womod

That's funny, there exists a similar issue with the LG G7 that a friend of mine ran into several years ago. The fingerprint sensor on his phone just straight-up completely stopped working, and subsequent OS updates did nothing to fix it. At first we assumed it was hardware failure, and he was ready to send it to a repair shop. While investigating it I saw a comment somewhere that it had something to do with the light sensor, and after holding my thumb over it for 10 seconds it "magically" started working again after 4 months of being completely non-functional.