Can't connect to SSL VPN before windows login

[Jconnelly]

I'm trying to enable the VPN before login option on forticlient SSL VPN. I have checked the box on the VPN settings to allow connection before login, however when users try to connect this way I get an error that the connection was refused.

We are using Forticlient 5.6.6, SSL VPN, and have the 'connect to vpn before login' option checked. Our PCs are Win10. The VPN is able to connect and login fine from the desktop, but I can't figure out what is preventing it at login.

Are there any specific ports or routes that this uses that I should verify are open? Any tips would be greatly appreciated. Thanks!