Cannot create child Apple ID
I'm trying to create an Apple ID for a child under 13 using Settings -> iCloud -> Family and the link at the bottom which says "Create an Apple ID for a child." I tap that, choose the birthdate, then agree to the EULA. The next page says "A credit card is required" and to "Go to iTunes & App Store Settings and tap on your Apple ID to add a valid credit card to your account." I already have a credit card on file and it is valid so I'm not sure where to go from here. It's just stuck.
iPhone 5, iOS 8