Refund not Processing for Credit Card Orders

[davidr_kai]

I have a customer where I am trying to refund shipping when it's less than what was charged to the card.  It refunds for orders that are paid via Payment on Account; however, ones paid via credit card do not.  They are using Sage Payment Solutions to process credit cards.  When I test on my development system it refunds without problems even for CC orders.  I have compared the refund request arrays and noticed that on the refunds that work the transaction section is populated; however, on the ones that do not the transaction section is empty.

I'm guessing it's a problem with the way Sage Payment Solutions is charging the card in Shopify, but I'm not sure how to confirm my hunch.  Has anyone ever run into this same problem?  Or provide any other insight into what may be going wrong.

Thanks.