Payments may fail for a number of reasons. Before/when purchasing, please always ensure that you have a steady internet connection and there are sufficient funds in the account associated with the card you are using.
Please make sure to double-check all your card information, including zip/post code of your billing address, is correct. In addition, double-check that the card you are trying to use has not expired.
In most cases, if all the information you are providing is correct but your card is still being declined, this would be due to your bank rejecting the payment.
This might be because they do not recognise our domain and/or are not sure whether you are the person trying to complete this transaction.
If you find yourself in this situation we would recommend trying to use another card (or PayPal), or ringing your bank to tell them that you are making this transaction before you try again.