Ack! Sorry!
Somehow I had completely messed up the Sign In system for Github and Google Users - which may explain the lack of new Google users when there had been quite an influx... This is now fixed.
Also, there was an error in the Analytics section of the code which was causing everything else to break - in particular the Forgot Password section which wasn't working properly. I believe this is now fixed too.
Apologies for that - teething issues of converting to a new authentication system. My fault, not the authentication system!