I had to request the password reset from Google after a few wrong entries. Haven't had a problem since, fingers crossed. Was worried when it happened though.
Re: My galaxy S6 doesn't recognize my fingerprints and asking for backup password
Believe it has to do with the recent Samsung software updates affecting the fingerprint reader. Happened to me also. Restarted device and still could not get in. After fourth or fifth mistake it comes up with...