The reason why the payment system doesn't accept a specific type of card is the following:

Our payment page has a card verification system based on the international card numbers. This validation allows to identify the type of card according to the different accepted payment methods: Visa, Visa Electron, Visa Debit, MasterCard Credit o MasterCard Debit / Maestro. In case the verification system detects that the payment method is not correct, an error message will immediately appear. You can contact your bank for further information about your type of card.