Greetings! I'm having this same exact issue with my students.
No audio will play on Chrome (even when C3 installed as app), Firefox or Edge. Not on preview, not when exported. Firefox console shows no errors.
I took an audio file (town.webm) from the Demonoire template (where audio works) to make sure it wasn't the file. Nothing.
Tried making the sound play on button push, to make sure it wasn't auto-play related. Still nothing.
I tried preloading the audio and/or unchecking preload, but that did nothing either.
Any ideas?
Thanks!