I used to be able to purchase HD movies from Apple TV. Now only SD is offered. Why did it change?

I currently have the Apple TV, 3rd Generation, and the software is up to date according to AppleTV Update. I used to be able to purchase HD movies directly from my Apple TV. Now only SD movies are offered on the Apple TV, which don't include extra features as advertised on Apple TV. What changed? How can I change it back? I looked for troubleshooting options and didn't find any.