If you are paying by credit card and it's getting declined and you know you have money in the bank, the reason it's most likely not working is due to an AVS mismatch. AVS stands for Address Verification Service.

When you submit a payment via credit card, it checks that your address on file with us matches the one you have on file with your bank. In the event it doesn't match, it will decline your transaction.

AVS checking is done for fraud protection services, if someone were to get a hold of your credit card, they would need to know your address as well in order to successfully use your card.  

If you feel that your address is not the same, please update your address information within the customer portal and re-submit payment. If it's still not going through after the address change, please open a support ticket and we'll be glad to assist further.