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If a member registers using Facebook connect and later uses another device that does NOT have the users Facebook information loaded; what do you use in the username & password fields to login to Jomsocial?
they still can login, the browser will be asked them to authentication via facebook in website version. same like if you using computer.
alternatively, user can reset its password and login normally through Joomla login forms, but as soon as FBC is used again, password gets reseted by random string.
I think I am understanding you but let me clarify.
A user can NOT simply login with a username and password if they chose Facebook connect.
This is problematic - If someone were to go to a different computer and did NOT want to login to Facebook but wanted to login to my site; what is the process?
Sounds like Facebook Login might not be a very wise move. If user were to login on a mobile device, is Facebook still required?