hello, is there a way to quickly change the PO Approver? I changed the PO Approver on each employee record; however, the PO's that were created before the change still showed the previous approver and the new approver cannot approve the PO's.

is there any workflow attached to it by any chance?

No there is not.

in that case just update the PO and resubmit it will sync

Strange that you have to do that but it did work! Thanks @Sam-I-Am

it worked because reference to database got updated when you open the PO in edit mode and submitted it updated the DB table. If there were workflow(suiteapproval) involved workflow would have routed the PO to correct person when user records gets updated.