Hey there, thank you for your report!
So, if I understand correctly, the buttons show up but cannot be clicked on?
I cannot get the issue to occur on my own Mac computers-- but one thing you can try is simply reinstalling.
If that doesn't work, can you answer a couple questions for me?
1. What version of Mac OS do you have?
2. Do you usually install using the itch.io app, or simply download from the JG web page?
I look forward to fixing this for you, sorry for the trouble.