There doesn't seem to be any way to report bugs like this so I'll post
it here: Installing the free FortiClient VPN under Windows 11 fails with
the nonsensical error message "FortiClient VPN requires Windows 10 or
higher". This is due to a bug in the...
Version 7.4.0.1658, the latest one. To see the bug, temporarily disable
the Workstation service (which will cause NetWkstaGetInfo() to fail) and
try installing.