Please try this build that has a brand new SSL VPN driver: https://www.dropbox.com/sh/cb0j4pxw1f8nq84/AABHzZW1bpx1VjzYAmiK00S9a?dl=0
This is a VPN only installer, and the driver is not Microsoft-signed. So you need to click "Install" on the pop-up Windows.
After install, please do the following to change registry [HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Fortinet\FortiClient\Sslvpn] "FtsslVnicEnabled" to 1.
1. Shutdown FortiClient.
2. Run cmd.exe as administrator, then run "sc stop fortishield".
3. Change that registry value to 1.
Please note that upgrade from previous version and to future version are not supported. However, backup config from your old FortiClient shall most likely be compatible with this one.
Please give it a try and report any issue back to firstname.lastname@example.org