Afraid you seem to have uploaded the wrong file. You've uploaded only the executable found within a build. You should have zipped up the entire build folder and uploaded that as it contains the resources necessary to run the game.
Don't be discouraged though, just having entered, built something and uploaded it is more than most. Come back fighting next time & be sure to download the uploaded build to test it once you've submitted. Submitting early and testing your build allows you to catch issues like this & you can upload as many builds as you like until the deadline expires.