In JFBConnect > Configuration > General area, please try setting our 'Skip Joomla User Activation' to No. Then in the options for Joomla Users Manager, make sure to enable the 'New User Account Activation' setting as well. This should give you the option to log in via Facebook but still require the user to be activated. Of course, if you've tried these settings already and are having issues, please let us know.
-Melissa