now whether this was the right thing to do or not.
- renamed auth_module.totp to auth_module.totp.tmp which I found in /config/.storage
- rebooted the host.
- Logged in without being asked for the two-factor code.
- Enabled then Disabled the Authenticator app through the GUI
- Saw that the original file auth_module.totp has been recreated.
All seems fine now.
Mike