Enable Existing Organization as Supplier

I require to enable a customer as supplier where trading partner is both.

I have seen the functionality described in the Supplier Management User Guide whereby in the Profile Manager it is possible to query the customer and then select the Enable as Supplier button. In my profile management screen, it is not possible to query back a customer (I use registry id) and the Enable as Supplier buttone does not appear. The only button that appears is the Create Supplier button.

i've also seen a note on Metalink saying that an existing supplier can be queried back in the customer screen and an account created for them - however, again using Regiostry Id, the supplier is not found.