Sometimes Vendors have issues finding their POs in the system. This article contains some common reasons why the POs might not appear in the Vendor side.
No matching results. Sometimes, the combination used on the search fields does not match any of the POs in the system.
Unapproved POs. Purchase Orders that the importer has not approved will not show on the Vendor's side.
Shipped POs: Once a Purchase Order is associated with an AWB, it won't show on the "Pending Orders" list anymore.
Wrong Company. Vendors can deal with multiple companies, which means that once they log in to the system, they have to select one of the companies from the list. The problem could be that you are looking for POs that come from a different company.