Ok, I tried some things out.
There is no 3D sound, no sound mix…just one plain vanilla mp3 file playing on a loop.
The issue is with Chrome, so the first item is N/A.
The site (Sketchfab) is not muted in Chrome.
All sites are allowed to play audio in Chrome.
I tried muting/unmuting another site (YouTube) which was successful.
For iOS, it works fine in Safari and the Sketchfab app, but in Chrome both the mobile version and desktop version of the web page are extremely intermittent for sound (ie. I’ve heard it only once or twice, most of the time NO SOUND.
I hope that helps a bit. I’ll see if I can try it out on a few other boxes here as well.