Do as it instructs. Tap "Continue" at the top right, or go back to you home screen and tap: Settings > [your name at the top] > Media & Purchases > View Account > Review Apple ID and check your payment information is current. Even if you only want something that is free, resolving any payment issue will be required if you already have any payment form on record.
- Are you (still) using a valid payment method? --> Payment methods that you can use with your Apple ID - Payment methods that you can use with your Apple ID - Apple Support
- If your payment method is declined, or you have a billing issue with a previous purchase in the iTunes Store - If your payment method is declined in the App Store or iTunes Store - Apple Support - various reasons why payment method is declined.
- If this abruptly started happening try removing and re-entering your payment information -
Remove a payment method --> Remove a payment method from your Apple ID - Apple Support
Add a payment method to your Apple ID - Add a payment method to your Apple ID - Apple Support
- Do the name, address (all spelling, letter case and punctuation), and card numbers exactly match those you have entered? You didn't mis-type anything?
- You entered the 3 digit security code for the card? Correctly?
- Acceptance may be easier if the country for the bank and your address are the same as the iTunes Store country you are using. (Apple does not, in fact, say anywhere in its support documentation that this is a requirement, only "You might need to ask your financial institution to allow international purchases on your debit or credit card" in: If your payment method is declined in the App Store or iTunes Store - Apple Support )
- See the end of the document linked above for special measures that may be necessary for some cards, plus about contacting your financial institution to make sure your records match.
If you still have a problem ask Apple at "Billing and subscriptions" support, click here ➞ https://getsupport.apple.com/?caller=cups&PGF=PGF63006&category_id=SC0060
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