I also had the same issue. I use firefox for itch games. When I open my web console I do see a few errors pop up that look like they are related to the game. there's a couple more that couldn't fit into the screenshot, but there's several calls on sprites not working, and other stuff like that. I'm not sure what's causing the issue though, since it seems to work on some computers and not others, but hopefully this points you into the right direction. 
