My iTunes U videos are not playing

So I found that there are all these free classes from amazing colleges that I can watch from the app iTunes. I downloaded a few and then after downloading I found that I can not actually watch any of them. The videos have the little blue dot next to them, I guess like in iTunes when you have yet to view them and the little i button which displays the information of the video. There is no longer the option to download the video so then why am I unable to watch them. My iPhone was remind me to manage my storage as my iPhone's hard drive was full. I have tried deleting a bunch of other items on my iPhone to see if that would change something. Alas, selecting any of the downloaded videos in iTunes is the same. As soon as I tap the session iTunes U program instantly closes and I am left waiting to see if anything will start playing, only to free silly staring down at my iPhone which does nothing in response. Has anyone had a similar problem or knows of the solution? Any light shed on this situation would be greatly appreciated.