Forticlient Installer Fails and Rollsback

Please check the eventlog for more information to see with what error code the MSI-Installation fails.

Also try to run the msi with the following command line to generate a log file:

msiexec /i "PathToFortiClientInstaller.msi" /log "PathToTheLogFile.txt"

Post logfiles and potential messages from the event log here.

I have a very similar problem as you and as a result I'm unable to deploy forticlient to replace our current anyconnect service.  Like toddataralco I a 1603 error and install fails at the driver installation.  His install is throwing error 13 and 82 (The directory or file cannot be created) as indicated between lines 999 and 1027 in his log file.  My error code is 5 which is access denied.  I have had multiple versions of my custom installation created and I tried a previous version that used to work and it now doesn't.  Something must have changed in windows that causes this to fail.  Any help would greatly be appreciated because I want to finish this ssl vpn project.

I have the same issue when I try to installer the FortiClient for Windows 10.  I've  tried to attached the log file that was generated but your system won't allow the file as it's to large

We ended up disabling UAC and our anti-virus software and installing it.  Sometimes we would have to reboot as well.

I had this same message appear, what seemed to resolve it for me was deleting everything in my %temp% folder