Hi there,
This article also 'teaches' you how to change/update your payment information, such as your billing address that may not match with the card billing address, etc.
Here are all the reasons your payment method may be declined; please review them:
- Insufficient balance or account in arrears
- Account suspended for suspected fraud (not necessarily by you)
- Error in card number
- Wrong expiration date
- Wrong security (CVV) code
- Address in your iTunes account does not match exactly the billing address for the card
- The card was not issued in the country of the iTunes store
- You are connected through a VPN provider that does not terminate in the country of the iTunes store you are connected to.
- Your Apple ID has security issues (email address/phone number not confirmed, password needing to be changed, two factors authentication required, etc.)