Why did I get API error code 15004?

The Card Verification Value (CVV2/CSC) entered is different than the value on the card or the card expiry date is incorrect.

Here's how to resolve this issue:

Check that the credit card's CVV number was entered correctly. The length of the CVV number depends on the credit card type:
Visa, MasterCard, and Discover - three digits
American Express - four digits
Make sure the credit card's expiration date was entered correctly.
The expiration month must contain two digits (MM) between 1 and 12. Include a leading zero, if necessary (for example, 05 for May).
The expiration year must contain four digits (YYYY) and be equal to or greater than the current year.