Is the issue that it doesn't install? Games in draft are not yet supported by the itch app, see https://github.com/itchio/itch/issues/1080 - the problem will go away as soon as you publish the game.
Actually, I didn't bothered hitting the install button. Since it's a WebGL game, I thought that it would run on the app in the same fashion as the browser by displaying a rectangle with the game. =P
Now that the game is installed, it's working normally.