Reassign PO Buyer to new employee

Summary:

We had an employee who was the main PO Buyer for thousands of POs. He just left the company. Since he is still the Buyer of a PO, we are not able to create Change Orders. We tried to run the Reassign Purchasing Documents process to a new Buyer, but the new Buyer was hired in November, 2022. All POs created prior to that date will not reassign to this new Buyer. And now we are not able to create Change Orders. How to fix this?

BTW: The new Buyer can manually create a change order for a PO and change the Buyer to herself, even the PO was created prior to her starting with the company and that works. But we have thousands of POs, so we need a way to fix this via the Reassign Purchasing Documents process.