3174497 - Error: "You do not have permission to perform actions on this purchase order because you are not assigned to customer [your customer's name]."

Why can't I see a specific customer's purchase orders? I also see an error when performing actions on their orders:

Error: You do not have permission to perform actions on this purchase order because you are not assigned to customer [your customer's name].

admin, purchase order, customer assignment , KBA , SBN-AN-TX , Transaction Documents , SBN-AN-SCC , SAP Ariba Supply Chain Collaboration , SBN-AN-TX-POA , Transaction (Purchase Orders, Ship Notices & Goods Receipts) , How To