There are many reasons for as to why a credit/debit card transaction was declined, when the most common reason being the card issuer bank has stopped the transaction. This matter can usually be resolved by you simply calling your card issuer and approving the transaction.
Please also make sure that you have:
- Entered the correct expiry date
- Entered the correct CVV (the 3 digits on the back of your card)
- The card is still valid and not expired
- The card has not been reported as lost or stolen
- The card you are trying to use is approved for international use
- There are sufficient funds on the card