Error: The ship-to location (Value=101) does not match the ship-to location on the purchase order

I am getting the following error on receipts interfaced from a third party system. We changed the Ship-to at the header and line level to agree to the same ship to location on the PO, but we still can't get them to update the PO to reflect the receipt. Has anyone had this problem before and how do we go about correcting it. Any help would be appreciated. There may be a discrepancy between the requisition and the PO in some cases, but it still happens when they all reflect the same information.

Thank You,

Bob