Do you get any messages/warnings in the browser console?
I get the warning "ProcgenMansion.js:276 The devicemotion events are blocked by feature policy." with a link to a github page about policy controlled features in browsers.
No, this shouldn't be a problem. It's just a warning, I get it too and it doesn't prevent the generator from working in my browser (browsers - Chrome, Opera, Edge, Safari). Apparently, it just doesn't work for some people. The only idea I have for you is to try another browser, sorry. Later I'll try to build a native version.