I recently had to reinstall Windows 10 and everything else.  I had backup copies of all the files but nothing was "installed".

I started by running the install for the Games for Windows Live client.  It would not run. It came back with some sort of goofy "network error".

Then I tried running the install for Flight.  Of course, it would not run because the GFWL Client was not installed.

Then I tried running Stonelance's install for the Toolkit.  It wouldn't run because it couldn't find "Flight.exe".

After this Flight seems to be dead and buried.

As a sidenote but worth mentioning, I reinstalled Microsoft FSX from CD and it installed fine but you can't use it until you register the copy.  When I try to register it that fails.  It comes back with the same goofy "network error".  New installs of Microsoft FSX seem to be dead.  FSX Steam Edition installs and runs like you would expect it to.

We seem to be limited to MSFS 2020 or FSX SE.

The same is for me - "I started by running the install for the Games for Windows Live client.  It would not run. It came back with some sort of goofy "network error". Then I tried running the install for Flight.  Of course, it would not run because the GFWL Client was not installed.".

In my case I have to use Steam version as they replaced Games for Windows with Marketplace and as a result I lost my Games for Windows account, passwords, codes and everything as well. So, I have a Steam Flight with all the DLCs "installed" according to Steam and I am not able to play "my" DLCs - I have only base pack - 2 planes and one island.