I had to switch off silent mode on iPhone for audio to work. Any chance it’s the same issue for you?
That's very strange though, I wonder if it uses a weird sort of web calling API or something for the audio. I've never had an issue with audio in web pages before, and even the youtube video the page embeds sounds fine. It seems quite poor UX (of Safari? Chrome?) to require turning off silent mode – many people never turn it off so it's not very discoverable, and then forgetting to turn it back on again could be pretty bad.
I run a website with music education tools and we had to make a dedicated help page for this particular annoyance:
https://www.soundslice.com/help/en/player/troubleshooting/23...