I don't get how Facebook Login works

Hi.

I think I have everything well configured (template options, facebook plugin, facebook API...) and when I try to login with Facebook, everything works fine. The e-mail of facebook account is the username in Joomla, and that username is added to the Joomla users list. Everything seems fine.

But what happens when the user sign off and wants to return later?

If he signs off, and returns later, if he press the Facebook Login button, the system will try to add the new user again, instead of just logging him in. Off course, the e-mais is already registered, and he get the "invalid e-mail" error. That's what is happening to me.

Can someone explain this to me? I don't get how it's supposed to work. Thanks!

Edit: I'm using J1.7

Ok, it looks like it works the way I said.

But in template Social API options, I wrote pt-PT in language field (like I'm used to in joomla language files), but it has to be pt_pT instead.

Or en_GB, es_ES, fr_FR... whatever you want, but always with "_"