How to validate a Supplier Punchout Payload?

Summary:

We are trying to create Punchout Requisitions for Inventory Items, and we are using a CPA

Content (required):

Whe we receive the payload, the punchout requisition line is created but the Aggreement and suggested Supplier are blank and if we try to process manually the requisition line we get this error:

"Requisition XXXXXX, Line 2: You can't add this requisition line to the order. (PO-2055338)

The requisition line is for a supplier configuration and the supplier and the supplier site of the configuration is different from the order's supplier or supplier site."

So, we'd like to know if there is a way to validate the payload? Just to know if supplier needs to add any attribute or, if supplier has any error.