Delivered workflow name for EDI PO order acknowledgements

Does anyone know the workflow that is delivered for the PO order acknowledgements? Right now, if an IDoc (basic type ORDERS01 for Message type ORDRDP) comes into our SAP system, if the IDoc has an error because of a u/m problem price change, or quantity, the IDoc goes into a '51' status but it does not get routed to the user ID on the WE20 set-up (it is not in my SBWP SAP Inbox)