You may need to advise your card issuer that you wish to make an international purchase and request that they activate Cross Border Payments (CBP). This can be done by calling the number which can be usually be found on the rear of the card.
Please double check that you have entered your card details correctly. The card you are using must be registered to the billing details otherwise this may cause your payment to be declined.
CBP is the reason for card failure in around 80-90% of cases so please do ensure that you have informed the bank that you are making an online purchase from Europe and retry before submitting a ticket or attempting to contact us.
If you are using a pre-paid card please see this article.
If you are 100% sure that you have entered all details correctly and you still cant resolve the problem then please contact us using our Live Chat facility or by raising a support ticket and we will try to assist you.
If you are using an alternative payment method then please contact us for further assistance.