Check Settings, Your Name, Payments and shpping
Is the card still valid?
Reasons your payment card may be declined
- Account suspended for suspected fraud.
- Address in your iTunes account does not match exactly the billing address for the card
- Error in credit card number
- Insufficient balance or you still owe money on a subscription
- The card was not issued in the country of the iTunes store
- Wrong expiration date
- Wrong security (CVV) code
- You are connected through a VPN provider that makes iTunes think you live elsewhere - uninstall VPN
Here is additional information from Apple if your payment method is declined.
If your payment method is declined in the App Store or iTunes Store - Apple Support