My producer got a free copy of Kontakt. He has the license for the two session player guitars I transferred to him. How does he actually upload them and use them. The only options he's seeing is pay for.
If he's added the licence to his account they should appear in Native Access. The first thing to check is that the products show in his account online on this page - https://www.native-instruments.com/en/my-account/my-products-serials-downloads/ Assuming that the products show there he needs to be sure he's using the latest version of Native Access and logging in with the correct username/password.
If the products don't show in his account and he's tried to import the Transfer ID for the products, or if the products do show up online but not in Native Access then his best bet is to contact NI Support here - https://bit.ly/NI_Support_All