Thank you for your response. (For users who are looking for the solution, skip to the bottom of my reply)

Below are things that I have done during my support case with Sophos directly.

1. I ensured that the Sophos Connect VPN client software is up to date
2. I ran the software as an administrator
3. I created a local Windows user account, which works, but that is not the point
4. I ensured all 3 dependent services are running: OpenVPN Service, Sophos Connect Service, strongSwan IPsec Service
5. I restarted all 3 of the dependent services, which were previously running
6. I uninstalled and reinstalled the Sophos Connect VPN client software, deleted all program files and app data, and removed the registry entries
7. I, temporarily, uninstalled and disabled cybersecurity software
8. I performed a Windows os reinstall, this is not the "Reset PC" it was the "Reinstall Now" option under System -> Recovery
9. The issue was not unique to 1 device or 1 user. It was experienced on at least 2 different users and 3 different devices running Windows 11 (Home and Pro)
10. I ensured the tap driver was installed
11. I ensured the tap driver registry key was present
12. I ensured there is no firewall rule that would block the Sophos Connect software
13. I ensured there are not group policies that would limit the Sophos Connect software

This issue pertains to the Sophos GUI not being able to get the connection state. There is an event handler that throws the "Service Unavailable" message when the connection state indicates no service. For those who are curious, you can look through the .js files of the program you can find the event handler to which I'm referring.

As mentioned in my first post, Sophos support was able to very recently (~28-May-2024) able to get the Sophos Connect VPN client software to install on a virtual machine with Windows OS installed. So, I was very perplexed and decided to create this post after Sophos support requested I bring this issue to Microsoft support for a solution.

Last night I experienced an issue where the Microsoft Store could not access the internet, regardless of how much I reset it. Therefore, I tried performing a complete "Reset PC" where it deletes all apps and data along with reinstalling Windows. I selected a cloud install so the latest version of Windows would be used for the PC reset. After the PC reset and initialization was complete the Microsoft Store worked again. Then, I thought to try installing the Sophos Connect VPN client software to see if the result is any different. And, sure enough, the Sophos Connect VPN client software installed and ran correctly, able to import a VPN connection config file normally. I even restarted the computer just to make sure the solution was stable, and it is.

SOLUTION:

For users experiencing this issue, try performing a complete "Reset PC" routine where all apps and data are deleted. Also, ensure the cloud installation is selected so the most current version of Windows is installed.

Probable Root Cause:

I suspect the probable root cause is a past Windows 11 update/version that either accidentally blocked/broke access to the Sophos connect dependent services or an artifact was left behind by one of these updates/versions that accidentally blocked/broke access to the Sophos connect dependent services. However, I don't have an official root cause from Sophos or Microsoft at this point, so it is just a good guess based on the solution that worked.

Thank you for your support. Please continue to improve communication with your technology partners so these kinds of issues can be resolved quicker and with more precise (less broad) solutions. Our business was negatively impacted by this issue and considerable time was lost trying to figure out a solution.