i dont know. try re-running the installer after removing the current one and see if that does anything
See this thread for a full log. The issue is that Spec Ops - Arrival is using an installer type not supported by https://itch.io/app
Shipping a portable version of the game (just a zipped .exe + data files) would work. In the meantime, app users can't play the game. See this page for details.