Hi Rambling,
I only have access to an older Macbook Air running OSX El Capitan. I tried it with Chrome (71.0.3578.98 - 64bit) and it seemed to work ok for me. itch.io launches the game in an iFrame and I am wondering if somehow its doing something weird in the OS/Browser version you currently have. Try again by clicking the mouse on the iFrame where the game is. If you hear music then it is in focus, if not, its probably focused on the parent frame I am guessing. Let us know. I can jump on a screen share and help troubleshoot on Discord