Apple says: "Some purchases might require that you have a credit card on file, even if you use your Apple ID balance to make the purchase." - from: What you can buy with your Apple ID balance --> https://support.apple.com/HT211187
For a variety of reasons Apple will almost always require a functioning payment method such as a credit or debit card be present when downloading anything from the iTunes or App Stores that isn't totally free (so, for example, a "free trial" that turns into a paid subscription isn't ' free'), even if the item will be paid for with Apple Account balance. The only solution to satisfy this requirement is to add a valid payment method*.
This document explains how to 'Change, add, [review,] or remove Apple ID payment methods' on a Mac or Apple mobile devices; click here --> https://support.apple.com/HT201266
Change your Apple ID payment method if you don't have an Apple device --> https://support.apple.com/HT210755 - PC, MS Surface, Android, Chromebook, online at tv.apple.com
'If you can't remove your last payment method or use no payment method with your Apple ID' click here --> https://support.apple.com/HT203905
- When updating an old card and have ongoing subscriptions, or are the organizer of a Family Sharing group, you may need to first add the new card and make it the primary payment method before deleting the old card.
- A payment method is required if you're using your account with the App Store for the first time.
If you still have problems, click here --> https://support.apple.com/choose-country-region/media-services Select your country, then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.
or:
Contact Apple for support and service --> "See a list of Apple phone numbers around the world." - https://support.apple.com/HT201232
Additional resources:
*'Payment methods that you can use with your Apple ID' --> https://support.apple.com/HT202631
