This project is invalid or corrupt and cannot be opened. It may have been created in an earlier version of Storyline.

Had the same problem. Seems to be a software issue. And a major one! New releases of Storyline doesn't support older files 100%. The file was made five months ago with 360. I tore my hair, trying to open 3 different backup versions before reverting to a Storyline version that was released five months ago. 

/David