Error: The Intercompany Transaction requires Invoice and a Supplier Association does not exist betwe

Error: The Intercompany Transaction requires Invoice and a Supplier Association does not exist between the Recipient Organization and Initiator Organization.

The start date on the Supplier is before the transaction so this is fine, the Customer and Supplier association are set-up correctly. Can somebody let me know what else could be the problem.

I have deleted the association and assigned it again and we are still having problems.