iTunes won’t accept PayPal when upgrading Keeper from Apple Store
Trying to pay for Keeper upgrade with PayPal. Won’t accept it.
What happens when you try to add PayPal? Error message(s)?
Apple ID payment information - change
Apple ID - Payment methods that you can use with your Apple ID
If necessary, contact iTunes Support. Either use the form or scroll to the bottom of the page in the 2nd link. Follow through the screens to get a chat or telephone option.