Please refer to the following information:

1) check the card details to make sure the information is correct. e.g. the expiry date or your billing address. (Common problems including incorrectly spelled name)

2) make sure you enter the security code correctly - that's the three-digit numbers on the back of your card. 

3) your card issuer may have declined your payment – please contact the card-issuing bank.

If the above information still does not work, you may try to pay it with another payment method – or using PayPal which is more convenient and safe!