Hey, I know why! I'm guessing you're probably using the zip file Mac version? If so, you'll have to follow these instructions here to get it to work on your computer. The game isn't actually corrupted, it's just that Macs aren't nice to games that aren't downloaded through their app store unfortunately. Sorry about that! It's possible that the .dmg version won't give you that error and you won't have to do any extra steps, but I don't know for sure.