During checkout if you experience problmes, several of the most common errors and reasons are here

Error Code	Short Message	Short Message	Long Message
15004	Gateway Decline	This transaction cannot be processed. Please enter a valid Credit Card Verification Number.	The transaction was declined because the CVV entered does not match the credit card.
15005	Processor Decline	This transaction cannot be processed.	The transaction was declined by the issuing bank,not PayPal. The merchant should attempt another card
10541	Gateway Decline	This transaction cannot be processed. Please enter a valid credit card number and type.	The credit card entered is currently restricted by PayPal. Contact PayPal for more information.
10554	Filter Decline	This transaction cannot be processed.	The transaction was declined because of a merchant risk filter for AVS. Specifically, the merchant has set to decline transaction when the AVS returned a no match (AVS = N)
10752	Gateway Decline	This transaction cannot be processed.	Possible causes of 10752 include: There was a problem with the CVV2 or AVS on the card. There is a problem with the buyer. The transaction was denied by the credit card's issuing bank. The transaction was considered to be of too high risk. The best way to deal with the error is to inspect the CVV2 and AVS codes that are returned along with the 10752 error. If the buyer's transaction has been denied, the buyer may still be able to perform the transaction by using a different credit card.

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