The FortiSSLVPN UI for the Gnome Network Manager was a great add. Unfortunately, it does not prompt the user for the 2factor authentication token that the underlying call to openfortivpn requests.

Here's the journalctl output for the request, in case people are curious.

vpn-connection: Started the VPN service
vpn-connection: Saw the service appear; activating connection
vpn-connection: VPN connection: (ConnectInteractive) reply received
vpn-connection: VPN plugin: state changed: starting (3)
INFO: Connected to gateway.
2factor authentication token:
WARN:   Error issuing /remote/logincheck request
ERROR:  Could not authenticate to gateway (Permission denied).
INFO:   Closed connection to gateway.
INFO:   Logged out.
vpn-connection: VPN plugin: failed: connect-failed (1)

Steps to reproduce:
1. Set up a FortiNet SSL vpn with 2 factor authentication.
2. Attempt to connect to the vpngateway:port (with or without password)
3. Fill in your password when prompted if not done in step 2.
4. The VPN connection will fail instead of asking for your 2factor token.