When testing an PO approval workflow, once the PO should be routing to the purchasing approvers account, it is not appearing at all. I have set up the purchase approver in the employee record to reflect who the PO should be going to. Has anyone ever had to trouble shoot this before? I'm thinking it could be some setting in accounting preferences that's wrong that causing these PO's to not appear in the respective approvers account.

1st of all did you turn the approval routing for the PO in accounting preference? Once you have done so, there will be native next approver field will appear on PO. Set this field via workflow to your targeted approver record (based on your workflow action parameters/condition). Also there should be workflow generated buttons for approval and rejection specifically for the target approver(user) - define that in workflow action conditions. You can create a saved search as reminder to show the PO's needed approval on user's dashboard.