Troubleshooting Tip: FortiClient installation fail with error 'Failed to load difxapi.dll'

1. FortiClient installation failed and rolled back. Checking the FortiClient installation log can see the below error:
   
   

FCSetupWx: Failed to load C:\WINDOWS\system32\difxapi.dll
FCSetupWx: Failed to load C:\WINDOWS\system32\difxapi.dll
FCSetupWx(rollback): Failed to load C:\WINDOWS\system32\difxapi.dll
FCSetupWx(rollback): Failed to load C:\WINDOWS\system32\difxapi.dll
UPDATEFAILOVERPORT=;UPDATEFALLBACK=;UILEVEL=5;WANACCDBDIR=;
MSI (c) (A0:C8): Product: FortiClient -- Installation failed.

2. Copy this file from another machine with the same path 'C:\Windows\System32', and paste this file into the same folder of the current problematic machine. 
                                                             

   

    

    

3. Reinstall FortiClient and it should go through as normal.

    

Note that this issue usually happens to new machines, especially for Windows 11.