This happens when trying to refund a transaction that is connected to an old merchant account that is no longer connected to Luminate Online. The only way to refund this transaction using a previous merchant is if the merchant is still active in your account. This is because LO doesn't store any of the credit card info, it is stored with the merchant account. If there is no longer access to the old merchant account, the only way to refund the client would be to provide a check to the donor or some other form of online payment.