I have GMS2 and I think I know how to fix this. I think you submitted the project files instead of the game. to do this, go to the very top off your screen in Game maker with the project open and look for the button that looks like a box that says "create executable". GMS will probably recommend an installer but I would recommend making it a zip file. Then submit the zip. I thought since I had GMS I could try playing it but when it loaded the game didn't have a any files, not even a room. Maybe you can ask the people who hosted this jam for permission to try submitting again. Wish you luck and I hope this helps! If you have the time try checking out my game, I also used GMS2. (-: