Hmm, Pierre is usually the expert in this kind of thing, but he's busy trying to get more sim missions scoreboard-enabled for our next release. Let's see if I can help.
So, you do have compatibility mode set on Standoff.exe and you have already tried to run the game by double clicking this file instead of using the Launcher or the shortcuts that are created by the installation?
If so, can you reinstall the game, choose not to run it at the end of the installation, and then try the above? I'd be interested to know if it still acts the same (works for the first time and then stops working) even when you launch it by double clicking the Standoff.exe file directly, ever since the first attempt to run it.