Why is it suddenly locking me out?

I’ve been using godot for about a week now, and it’s been going well. I even made a beginner tutorial world. Now, I’m working on a jam to get myself really fired up

But everytime I open the program, it’s saying ‘error, no main scene selected.’ What?? I’m just trying to get in the app! I can’t even get in to get into a project that would or would not have a scene! I tried to redownload it, but SAME problem! (I’m using Linux on a shit Chromebook but I really don’t think that’s the problem for once)