How to properly diagnose Windows 10 pro firewall not functioning

Ok, macOS / Linux native here on Windows territory and a bit lost.

I'm helping a family friend upgrade to Windows 10. He has a company laptop that he was allowed to keep after his retirement. It had Windows 7 Pro on it. I upgraded it via Microsofts own Upgrade application and it worked great. All files/folders still in place and all applications working smoothly, except for the Windows (Defender) Firewall:

• When I look at the firewall setting in the renewed settings menu it is set to "off" and the button is greyed out.
• In the configuration screen -> firewall settings there is an exclamation mark with a warning message that the firewall isn't set to it's default settings. There is also a button to restore the default setting but pressing it throws an errorcode 0x80070437

• Within the Windows 10 settings app there is also a firewall status screen that shows:

• I tried logging into the administrator account to press the same button but same error persists.
• I downloaded & ran the "Windows Firewall Troubleshooter" program but it also failed to solve the problems. In the detailed report it read:

"Windows could not start the Windows Firewall on Local Computer"

• I tried running services.msc and starting the Windows Defender Firewall service from there but it keeps shutting itself down directly after it starts.
• Finally I tried restting the service via CommandPrompt (run as Administrator) using the command Netsh advfirewall reset but it returns:

EDIT 1

By advice of @harrymc I also tried the solution offered here which boils down to giving the “NT Service\MpsSvc” account adequate permissions, but the errors still persist..

I am left without a clue as to what I can do to further diagnose the problem?