I couldn't get your page to load to test, but if you're getting a pop-up error when you try to click "Send Invitations", you're likely affected by the bug in the post below (with solution):
www.sourcecoast.com/forums/jfbconnect/jf...t-working?p=1#p14716
If that's not the case, check to make sure that you've disabled JomSocial's Facebook integration, as that can cause some issues. You shouldn't have any API/Secret key in JomSocial's Facebook Connect area.
If it still doesn't work, can you explain more about what's happening? When you click the button, is there no response? Do invites simply not get sent? Are you redirected anywhere, etc?
Thanks,
Alex