File Unable to Open

A piece I have been working on for the past couple months will not open anymore. I was working on the score and trying to save my progress when it said unable to save. I re-saved the entire file and replaced it in my downloads but now it says "Cannot read file". All of my other scores seem to open fine except for that one. I also work on a Macbook Air. I am a Music Composition student and this piece is part of my grade, so I really need it to open because it's important.