Hello aWinsnes,
Thanks for using Apple Support Communities.
I see that you are having an issue with the iTunes Store downloading movies and TV episodes after the rental has expired. And you are also getting a message that the download can't be completed. I know how important it is to make sure you are able to download and view the content that you requested. I'll be more than happy to assist you with this.
First, please give your iPad a fresh restart and then test again to see if you get the same result. This article will help:
Restart your iPhone, iPad, or iPod touch
Next, sign out of the iTunes and App Stores, and then test again to see if you get the same result with downloading after the rental has expired, and with the download can't be completed message. You can sign out and back in by following this path: Settings > iTunes & App Stores > Tap Apple ID at the top > Sign Out.
Also, check out If an iTunes Store purchase unexpectedly stops downloading, and see if you can restart the download that can't be completed, specifically, this section:
On an iPhone, iPad, or iPod touch
- Open the iTunes Store app.
- On your iPhone or iPod touch, tap More at the bottom of the screen. Then tap Downloads.
On your iPad, tap Downloads. - If prompted, enter your Apple ID and password.
- Find the item that you want to resume downloading, and tap the blue download arrow
.

If you can't complete the download on your iPhone, iPad, or iPod touch, download it in iTunes on your Mac or PC. Then sync it to your device.
You can also transfer purchases from your iPhone, iPad, or iPod to a computer.
If you still can't restart your downloads, get more help.
Cheers!