Unable to install FortiClient VPN 7.4.3 Win Arm

Hi my collegue had the same problem but was able to overcome extracting the .msi file from the offline installer .exe and executing the msi file after manually installing the 2 vc_redist packages required for the forticlient.

HTH

I finally found a solution. Below are the steps I followed to resolve it. 

Cause

Using the wrong or outdated installer leaves traces of FortiClient that are not removed during the uninstallation process. Then, when attempting to install the correct version for ARM64, an error occurs, causing the installation to roll back. The error occurs because a mix of FortiClient drivers and files from different versions is created.

Solution

Since the FortiClient uninstallation process doesn't remove all files and references, a manual process is required. Below I describe the process that worked for me.

Step 1. Uninstall the incorrect version of FortiClient
At Control Panel > Add / Remove Programs, locate any installed FortiClient. Uninstall it. You'll need to restart Windows afterward.

Step 2. Manually uninstall FortiClient-related services
Go to Administrative Tools > Services and locate Forti-related services. 

Then, in a command prompt with administrator permissions, run the following command to uninstall services: (I'm using FortiClient VPN Service Scheduler as example)

sc delete FA_Scheduler

The service will not disappear until you restart Windows.

Step 3. Uninstall network devices related to FortiClient
In Device Manager, identify Fortinet network devices that could not be uninstalled. Perform a manual uninstallation of the driver (selecting the Attempt to Delete Driver option)

Step 4. Delete FortiClient Drivers Manually

In the Windows\system32\drivers folder, locate the FortiClient drivers and delete them manually.

They are all those that start with Forti, as well as ftsvnic.sys and ftvnic.sys. One of the latter is owned by TrustedInstaller, so you'll need to change the owner to your user to give yourself permission to delete it.

Step 5. Manually delete other FortiClient files

Delete a copy of the installer created in this path:

C:\ProgramData\Applications\Cache
C:\ProgramData\Applications\Cache\{15C7B361-A0B2-4E79-93E0-868B5000BA3F}\7.4.3.1790\FortiClientVPN.msi

Delete Fortinet folders located in these paths:
C:\Program Files\Common Files\Fortinet\
C:\Program Files\Fortinet\
C:\Program Files (x86)\Fortinet\

Step 6. Delete FortiClient registry keys
Use regedit to delete the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Fortinet
HKEY_CURRENT_USER\Software\Fortinet

A reboot is recommended after this step.

Step 7. Download the Correct Installer

The documentation I reviewed recommends downloading this FortiClient v7.4.3.1790 installer with native support for Windows ARM64. This installer should be available on the Fortinet portal under the name
FortiClientVPNSetup_7.4.3.1790_ARM64.exe

More info here FortiClient Support for ARM Architecture - Fortinet Community

I downloaded and used a copy of the installer published in this Reddit ARM support finally released for Forticlient : r/fortinet

If you're not comfortable using that source, you can use the installer for Windows 64-arm listed at Product Downloads | Fortinet Product Downloads | Support. I should work. 

Step 8. Install with administrator permissions

After following all the previous steps, the installer did not fail.

The installer is supposed to install several prerequisites:
- Visual C++ Redistributable for Visual Studio 2015–2022 for x64
- Visual C++ Redistributable for Visual Studio 2015–2022 for ARM64

In my case, it didn't, which is why, when I opened the FortiClient application, I got the error (I saw it in Event Viewer > Windows Logs > System):

Event ID 26, Application Popup. Application Popup: FortiClient.exe - Application Error: The application was unable to start correctly (0xc000007b).

If this happens to you, download and run these Visual C++ installers directly from the Microsoft website.

Forticlient should work after that. 

GoodLuck!!