I was experiencing a load of problems while trying to map FB users to Joomla users via the "connect" button on SC Login.
After a while I notice it was missing the scope atribute.
So, I edited the mod_sclogin/helper.php file, around line 336 (function getJFBCConnectButton):
Changed
$buttonHtml .= '' . JText::_('MOD_SCLOGIN_CONNECT_BUTTON') .'';
to
$buttonHtml .= '' . JText::_('MOD_SCLOGIN_CONNECT_BUTTON') .'';
As you can seen its a quick patch, since to be properly done one should read the required scope from FBJConnect settings - I just typed in the ones I need

.
But now I got it working