The most likely reason a credit card is rejected by our system is that your bank rejected our verification request. Please call us at 800-865-7496 so we can try to verify it directly in our system. Another problem could be if you are using a debit card. We accept checkcards, but not debit cards since they require a PIN.
One more thing to try, is to try again. It could simply be an address mis-match, or something else that was not entered correctly the first time.