If you see "Access Denied" on a driver, reboot into and run the command again.
Are you getting a when trying to uninstall via the Control Panel?
Sarah logged into the support portal, verified her credentials, and downloaded the latest version of the tool. She booted the laptop into —the only place where the tool can truly work its magic without the FortiClient self-protection drivers fighting back.
A failed upgrade left FortiClient in a half-installed state. Services won't start, but the MSI package thinks it's installed. Normal uninstallers crash. Exclusive mode cleans the slate.