That restriction has likely been placed due to the "Post on Register" or "Post on Login" message configuration settings. Facebook changed their API policies at the beginning of this year to clarify that you should not post messages automatically to a user's wall in the way JFBConnect has been doing it for those events. Basically, they want you to show the user a prompt to have that posted to their wall (so they are opting-in).
That's not something JFBConnect does, though it's something we're investigating. At the top of the Post To Wall configuration area, there is a note about this change and recommending against it's use. However, we left it in the latest release due to the newness of the change and to give our users time to adjust.
The reason Facebook does not want those types of feed posts anymore is because they want apps to move to using Open Graph Actions, something JFBConnect fully supports. These are automatic actions that can be posted to a user's FB Activity Log when they 'do' things on your site. However, Facebook explicitly states that actions should not be posted for merely registering or logging in.
So, in short, that feature will likely (and unfortunately) be removed over the next few releases as it is. We are looking into a way to 'popup' a prompt to let the user post to that they registered, but I can't guarantee if that will be possible or when it would be available.
I hope that helps, but if you have any questions, just let us know.
Thanks,
Alex
My Facebook App Has Been Restricted
