Rental movies won't download or play

I rented a couple movies through iTunes via my ipad. The movies don't complete downloading and I'm unable to play them. They are in my rentals available, but when I try to play them I get an error. When I go back to iTunes to rent them again I can't, instead of the rental icon, a "watch" icon exists. In my rentals, i push the "cloud" icon and I get a message that I rented the movie but it is not downloaded and recommends I go to downloads to restart. In iTunes there is no downloads icon available. I can't re-rent it, download it or watch it.