error closing work order

I'm receiving a different error trying to close the work order in my testing environment 'a sub-contract operation is ordered or in progress. closing not possible.'   The PO created from the work order has been received with same quantity as the WO and the PO is closed.   for some reason the Operation is not displaying the material as being achieved when the PO is received and closed.   I'm hoping someone can help me out with this.  thanks, Christine