Hey, I'm not sure why that's happening! Are you going through your library for things you own? if it's not showing up to download there, let me know, I can make you a DL link.
Ah, you know what? It looks like I can actually go to the download page and download it through my browser, but I can't install it through the app :/
When I try, there's nothing to select from the "Install" drop down menu. Is that just a problem with the app?
Ah, I'm actually not familiar with the app, but if you are able to download the game through your browser you can run it by just extracting the files from the zip and running the game application--it doesn't require an actual install process.