SUS - PO XML message error

Hello,

I am experiencing a problem with processing POs in SRM.

I have set up the plan-driven procurement scenario (MM-SUS) with ECC 5.0, XI 3.0 and SRM 4.0. SUS and SRM are on the same client.

When creating a purchase order in ECC, it arrives in SRM as I can see in the XML monitor. But the PO is not processed further. The error message is "Ordering party has to be a company".

I have checked the organizational model and settings for the XIAPPLUSER.

Does anyone have an idea where to continue investigating? Any help is much appreciated.

Thanks a lot and best regards,

Markus