...and to get a better answer to your question I would suggest you to consult an immigration attorney, or at least research this topic on official immigration services website (www.uscis.gov)....
(a) You made a typo in the card number, CCV code, expiration date, name or address;
(b) Your card balance is too low;
(c) Issuing bank has declined this transaction for some other reason related to your account.