itch.io

If you are trying to play it through the downloaded zip, I won't be much help since I played it through the Itch app. Maybe try that but no guarantees.

Did you try using some random RPGmaker game that can run on mac and then just swap main folder of this gamne to RPGmaker version mac? 

In your MacOS terminal: 

cd "/path to your folder that contains the game"
(use the quotation marks at the beginning and end of your path)

Then:

chmod +x "Game.app/Contents/MacOS/nwjs"

Next, right click and Open the game as you normally would. Then, select Done. Then, go to your Privacy and Security Settings and scroll down to "Security". There, select: "Open Anyway" --> "Open Anyway". After that, each time you launch it by clicking on the game normally, it should work. If that doesn't work, it means that your MacOS's Gatekeeper has quarantined the applicaiton. Can't help you with that.