Diagnosis
The commission contract partner has already been flagged for archivingfor the selected time period (effectively valid from - effectivelyvalid to). Therefore, you cannot create a new commission contract forthis commission contract partner.

Procedure
You need to select a different period of time for the commissioncontract, or remove the archiving indicator in the partner maintenance.You can find out the date from which the archiving indicator is set bylooking at the business partner maintenance or display. ChooseExtras -> Partner Changes.