I have a similar problem, but none of the above solutions has worked for me. I have forgotten the alternate password, and now the fingerprint scanner no longer recognizes my fingerprint! (I know I have used the same finger, but about every 3rd or 4th try, it says the print is unrecognized.) I can get in through my Google account, but long pressing on the saved fingerprint does nothing, and I see no other menu option. I went through android device manager, and was able to lock the phone and use a new password. On unlocking the phone, (again by Google because the scanner did not recognize the fingerprint and the alternate password did not work), I still cannot delete the saved fingerprint. Any ideas?