Billing verification
Put $25 iTunes card on account, but ask for billing information, then will not accept or allow me to purchase books
Apple TV, iOS 11.4.1
If you currently have a card on the account see if you can remove it : Change or remove your Apple ID payment information in the iTunes Store - Apple Support
When you have a card on an account it has to be a valid card and pass the iTunes validation, that applies even if the account's balance covers the total price of what you are trying to buy, or if the item is free to download