No instance of object type PurchaseOrder has been created. External reference poschedule

Hi Experts ,

I am trying to create a PO with respect to PR Using BAPI_PO_CREATE1 . The PR is created from third party Sales order

following error occourred attempting to creation

"No instance of object type PurchaseOrder has been created. External reference poschedule "

Please help me out ...

Kind Regards ,

Omprakash .😊