iOS Forticlient SSLVPN connection fails: Internal Error

[mackdav1]

I have the Forticlient SSLVPN client running on a selection of iDevices. When I go to connect to a SSLVPN connection hosted on a 200F running 7.2.4, the VPN comes up, then the client errors out with Error: Internal Error, and the VPN is dropped. There are no interesting droppings in the logs coming from the Fortigate. The logs show the connection, the tunnel coming up, and then the tunnel being brought down. If I deliberately mess up the login password, I get a different error, so it isn't an auth issue.

The same client can connect successfully to a similarly configured 300D running 6.4.11.

Windows 10 clients can connect to this 200F properly.

Does anyone know what the client is trying to tell me with "Internal error"?

[JimBennit]

Try changing the vpn listen port and see if it connects. My company spent a lot of time with support on this issue and this was the fix that worked for us.

[mackdav1 · Accepted solution]

So I upgraded the iOS client from the 6.0/Legacy client to the 7.x client, and it works now.