Hi there! We're you able to follow the steps in the link I posted in the game's description? Here's the link again to be specific: https://help.yoyogames.com/hc/en-us/articles/216753558-Mac-app-damaged-when-down...
If this didn't work, then from what I understand downloading through the itch app should work. Please let me know if you need any other help! :)