RSSP - Blank page when trying to bring items back from punch-out

Summary:

Is there a reason why some existing punch-outs which work fine in original SSP wont return items back to RSSP? I'm getting a blank screen rather than the item adding to the cart, however if I try from normal SSP and punchout, I'm able to return the same item without any issue.

Content (please ensure you mask any confidential information):

An existing punch-out which works as it should in SSP, does not work in RSSP. Presented with a blank page when attempting to return items to Cloud. Other punch-outs appear to be working without issue.

Version (include the version you are using, if applicable):