My account is configured with an electronic order routing method of Email, cXML, or EDI, but I do not receive certain purchase orders (POs).

Regardless of the routing method configured for your account, legacy POs are only routed to your Business Network Workbench.

You can click the Resend button at the top of legacy POs if you need to send a copy of the order via your configured order routing method.

The orders are designated by your buyer as legacy POs, which do not follow your configured electronic order routing method.

Buyers can upload previously fulfilled POs to allow their suppliers to invoice them via the SAP Business Network. Legacy POs can be identified by the comment This purchase order has already been fulfilled at the top of the order. These POs are intended for invoicing purposes only and should not be fulfilled again.

The Commerce Extensible Markup Language (cXML) file for the PO includes an AribaNetwork.LegacyOrders extrinsic element in the OrderRequestHeader section which designates the order as a legacy PO:

<OrderRequestHeader orderDate="2020-01-22T13:04:04-08:00" orderID="PO123456">
...
<Extrinsic name="AribaNetwork.LegacyOrders"></Extrinsic>
...
</OrderRequestHeader>

The Business Network sets the status of the legacy PO to Sent/Unconfirmed.

EDI represents the Electronic Data Interchange routing method.

See also Why do I see a "Purchase order has already been fulfilled" message on my order? for additional information on legacy POs.

SAP Business Network for Procurement & Supply Chain > Administration (Buyer & Supplier Account Administration)