I am having subscription issues with iTunes U on iTunes 11.1.4. When I subscribe to a course, all of the details are blank with "unknown artist" and so on except for the course name, and file names of the materials. I just recently subscribed to four new courses and some of the materials are missing. It has been over a few hours with Internet access and iTunes running and the issue still persists. All of the lecture videos are missing. What is going on and how do I fix this?