If the User is attached to a multiple site organisation with a 'Parent' organisation, make sure the Supplier is loaded into the Accounts Payable Hub of the 'Child' organisation that is currently being used. If not, the Supplier will need to be added into the 'Child' organisation's Accounts Payable hub. Check out this article3 for more information, How to add a Supplier.
However, before adding a Supplier to the Accounts Payable hub, check with the Accounts Department of the organisation to see if the Supplier might already be listed under a different name, or have recently had a name change.
Please note, if the Supplier's ABN is already in use by another Supplier in the system, the details of the Supplier attached to the ABN will be used instead of what has been newly loaded, as Purchase Plus does not allow multiple Suppliers to share the same ABN.