You may receive this error if you are trying to refund a transaction that has already been refunded in the payment gateway. There can be communication issue between Luminate and the Payment gateway where a refund appears to have not been processed when it actually has. Login to your payment gateway and search for the transaction. If you find that a refund has already been processed, follow these steps to perform an offline refund in Luminate to correct the record.

If you do not know how to login to your payment gateway or how to search for a transaction, contact support and ask them to do this check for you.