How do I redeem movie rental credits I received years ago in iTunes?

How do I redeem movie rental credits I received years ago in iTunes? My Apple account shows that I have the 2 credits, but that info is grayed-out so I cannot access (click on) them. These are not codes or gift cards, so that method of redemption won't work. They do not automatically redeem when I go through the process to rent a movie w/AppleTV. It's like they are both in my account and also not. My payment methods for my account only include my credit card, and I did not find a way to add a payment option of using an existing account balance. Anyone run into this issue before?