I just got into your site, and made some minor changes. It's working now, and hopefully, my solution will work for you.
It seems like SEF Advance doesn't like the way that JFBConnect tries to return the user to the current page they are on. I updated JFBConnect's settings to always redirect the user to the Coupons page after logging in, and that fixes the issue. Of course, this means that the user does not remain on the same page they were on.
Unfortunately, I can't debug SEF Advance because it's encrypted. If you want to let them know about the issue, you can tell them that the way we're trying to redirect the user is as follows:
Get the address of the current page:
$return = $uri->toString(array('path', 'query'));
Then, perform a redirect using the controller "$controller->redirect($return);". This works for all other SEF components we've tested with, so hopefully they can help determine why it's not working in theirs.
Finally, and unrelated, while testing, I switched the permissions setting to require the email permission to register. Since you're using Facebook User Only, we'd recommend this setting. Without it, JFBConnect will simply make up an email address for the user, and you won't ever be able to contact them.
Hope this helps,
Alex