I haven't updated the files since almost 2 years (but maybe no one tried the Mac version?) For some reason itch.io won't let me download my own game XD So I can't check.
But can you re-download it and check the content of the package? That file should be there. I've checked my latest package and the file was inside.
Of course if you're running the executable directly without extracting everything, it won't work. If I remember correctly, normally you simply have to double click on the downloaded file and it should install. (but admettedly, I rarely use a Mac and my memories from two years ago are fuzzy)
Worst case scenario, you can get a Steam key, for which the Mac version definitely works.