This morning I restarted my iPhone 7 due to an unresponsive app - Facebook, which does not use Touch ID. On restart I had to enter my passcode, which was to be expected after a reboot.
I then tried to view some banking apps, which require Touch ID, the first required my passcode, rather than Touch ID, I thought this was strange, but carried on. The second banking app showed a Touch ID error. Going back to the first app showed the error below.
I have not made any changes to Touch ID since setting up the phone months ago (at which point I filled all 5 slots for fingerprints), so am slightly concerned about this warning.
What could have caused this message? And what is the safest course of action?