You can try using the methods outlined here: https://itch.io/t/46387/how-to-download-and-instal... - While some info is PC specific, the itch.io client instructions should be generalized enough to follow. Using their download manager to install the game can sort out all sorts of issues. If you're already using the itch client, I'm afraid I don't know what to tell you. My test PCs all run windows, so as such I have zero Mac experience, but Doborog develops on a Mac, so maybe he can chime in if he knows. :-)
-Cheers