Q: Purchased a movie to rent and it won't download . Tried twice. What do I do ?

Hello, D Willy. 

Thank you for visiting Apple Support Communities. 

I would need a little more information on this issue to provide a better answer.  Any errors received would be helpful.  However, here is some information that can get you started troubleshooting this issue. 

Troubleshoot issues on an iPhone, iPad, or iPod touch

If you haven't been able to connect to the iTunes Store:

• Make sure your date, time, and time zone are correct in Settings > General > Date & Time.
  Note: Time Zone may list another city in your time zone.
• Make sure that your iOS software is up to date by tapping Settings > General > Software Update (iOS 5 or later) or connecting your iOS device to iTunes and clicking Check for Update on your device's Summary page.
• Check and verify that you're in range of a Wi-Fi router or base station. If you're on a device with cellular service, make sure that cellular data is turned on from Settings > General > Cellular.
  Note: If connected to cellular data, larger items may not download. You may need to connect to Wi-Fi to download apps, videos, and podcasts.
• Make sure that you have an active Internet connection. You can check the user guide for your device for help with connecting to the Internet.
• Make sure that other devices (portable computers, for example) are able to connect to the Wi-Fi network and access the Internet.
• Try resetting (turning off and then on again) your Wi-Fi router.
• If the issue persists, try troubleshooting your Wi-Fi networks and connections.

Can't connect to the iTunes Store

http://support.apple.com/kb/ts1368

If you were billed for this movie rental and are still unable to download this item, I would recommend reporting a problem with the purchase via the steps in the article below.

How to report an issue with your iTunes Store, App Store, Mac App Store, or iBooks Store purchase

http://support.apple.com/kb/ht1933

You can also report an issue with this purchase by accessing your purchases history in iTunes on your computer.

iTunes Store & Mac App Store: Seeing your purchase history and order numbers

http://support.apple.com/kb/HT2727

Cheers,

Jason H.