Error in bulk procurement agent import

Referencing KB144630 and KB120286 - I get the error: Status details: nullJBO-27014: Attribute PrcBuId in ProcurementAgentAssignmentEO is required. KB120286 references the same error where the solution is to "add buyer assignment in Procurement BU" but unsure of the steps to do this

Steps - export procurement agents set up file in Setup and Maintenance
-edit PO agent access file in notepad++ (changed one line for one agent from NONE to FULL and N to Y for granted access)
-compress xml and 2 csv files to a zip file
-run import from CSV file in Manage Procurement Agent action menu