enrollment request not accepted

I created a course on iTunes U and received an automated email informing me that I could view my class by clicking on the link.

I did, and then iTunes asked for my ID & password. I entered those and immediately received a pop-up message "enrollment request not accepted."

The course is set up to allow new requests. I've tried multiple times and changed the enroll code. Nothings works. There are no pending, enrolled or blocked students. Help?