Please be aware that you are not communicating with Apple when you post in these forums. Most of the people who will reply to your posts are, like me, your fellow users.
As to your issue, you had 30 days from the time you downloaded the rental, and 24 hours (US)/48 hours (rest of the world) after you first begin watching to complete watching the film. If you did not watch the film within those times, then the film has expired. If you still want to watch the film, you'll have to pay to rent it again, just as you would with any other item you rent that has reached its due date. If, however, the film disappeared before 30 days had elapsed, or before 24/48 hours after you began watching, go here:
and follow the instructions to report the issue to the iTunes Store.
As to your problem with your iPad, I'd suggest you take that up in the iPad forum. Be sure to include all the specifics so people have information on which to base a diagnosis and suggestions.