This has happened to me today as well, i got the phone friday morning and its worked fine all weekend but today it stopped recognising any of my recorded prints
I cleared the prints and tried to record new ones and it took multiple attempts to get a successful print recorded (in the shop it took like 5 taps to get the whole print then moved onto edging) but now it more often than not fails to record a whole print and i have to start again.
As of now i have no prints recorded and cant successfully record new ones (it gets the whole print other than one of the three central lines of the fingerprint and then refuses to store them right up until it fails)
During the process of troubleshooting this today the few times it has allowed me to record a print and enter the phone via touchid it has taken much longer to do so than it had been when it was working properly (4-5 seconds to successfully read the print)