Same I just downloaded it hours ago and tried opening it says it can't be opened I even went and played a few other VN's I had lined up to play after it and still won't open.
(EDIT)
So I found out by doing some digging in the comments and if you download the itch.io app and then download the game inside the app on your MacBook it opens up with no problems! I hope this was explained well for you guys and good luck with it!