I'm sorry to say that it might be that the graphics card on your machine doesn't work with WebGL 2.0. Could be the drivers but if they're up to date already there isn't much I can do to help you out sadly :(Maybe try it out on someone elses mahine?
I know my macOs is old. Maybe yes I will try it on another computer. Thank you! I love Hidden cat's graphic, I saw it in a video gameplayer :) bye