The credit card decline code “15: No Such Issuer” indicates that the credit card number entered does not correspond to any issuer recognized by the payment processor. This often happens when the credit card number is entered incorrectly or if the number does not follow the standard formatting for valid credit cards. Essentially, the payment system does not recognize the card-issuing bank based on the information provided, leading to the transaction being declined. If this error occurs, it’s advisable for the cardholder to double-check the card details entered and try again, or use a different card for the transaction.