Get Okta to work with our Fortinet VPN like DUO

We currently use DUO for our Fortinet VPN and that works flawlessly. But we are currently on a trial with Okta to get this to work and it's not going so well. We have been tossed around with multiple support engineers and even with Fortinet and no one can figure it out. We look at our Okta RADIUS server logs and it says Fortinet is changing out login username to test01. There is no such user! Okta said this is why it's not working. :( Someone must have this already setup. Someone please help!

****Okta and Fortinet cannot figure it out.