Jay,
Sorry you're running into some issues. If you're getting that error, it means one of a few things:
1) The Joomla user you selected hasn't authenticated on Facebook. I know you mentioned you did this, but please go to the JFBConnect -> Usermap area and find the Facebook user that you authenticated as and then click into their Joomla user. Make sure that Joomla account is the one you're selecting.
2) The Joomla user you're selecting hasn't authenticated via Facebook in a very long time. In that case, the access token to Facebook may have expired.
Please tell me if either of the above helps. If not, and you still have issues, let me know, and we'll gladly try to help narrow things down further. Another easy test is simply deleting the channel and trying to create it again. Not sure what could be gumming up the works, but it's worth a shot.
Thanks,
Alex