Can you tell me what the error says? Is it complier errors in your code?(That means it can't run without fixing your code). I think I need more explanation on this. Thanks

it always happen to me, sometime because i didn't close unity correctly, then i lose the progress and ihave to start from the beginning!!

Wow maybe that is the answer

Did remove the Library folder? Close unity, remove the library folder, then open your project up again - (of course you'll need to wait a while for your project to re-load.)

If it worked before, it's probably a corruption of some kind in Library,

I have actually come across this before, where the error showed and the scene was empty, and all I did was go into another scene and open the broken scene using the SceneManager.loadscene function in a script while playing in a working scene.  After that, it loaded and was fixed, although i dont know if that always works, or if it was really the same error, you probably messed around with it too much for it too work anymore but why not give it a shot.

next time i suggest to create a copy of the folder because im sure it's annoying