We were having many issues with a FortiClient VPN 7.0.1.0060 (free version) not being able to connect to our SSL VPN which uses username, password, and client certificate. The logs showed it connects then immediately disconnected. The paid FortiClient as well as the Windows version of the free FortiClient VPN worked fine with the same settings.
This was a MacOS issue. To fix:
go to Apple System Prefs -> Security and Privacy -> General -> Details ….
does anything in there say “Fortitray”?
if yes, tick the box, restart FortiClient.
and it should connect