First, make sure that you are using a valid credit card and that your card has not been disabled for any reason by your bank. If using a valid card, the system may not be accepting your payment due to a missmatching data requirement from the card. This is most likely due to an address verification missmatch, which is commonly related to the billing ZIP code associated with the card. Please verify that you are using the billing ZIP code tied to your credit card or debit card. This is the address in which your banking statement bill is mailed. You can often contact your bank or credit card company to confirm this information.