Dear Antonella, I don’t see any particular advantages or disadvantages of either LLC or S-Corp for your particular line of business, that is to say it’s the same advantages and/or...
(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.