Make sure that JFBConnect Authentication, User, and System plugins are enabled. Also, make sure the JFBConnect User plugin is ordered after (higher) than the Joomla User one.
If that's correct, then, in sh404 in the component configuration area, tell sh404 to 'skip' JFBConnect altogether.
If none of tat helps, please post your URL so we can get a glimpse of what's happening. Thanks!
Can't login through facebok after upgrading to the latest version
