I’m not familiar with Coverage nor can I find information about what it might be with google searches like “coverage html5”. Can you provide a link to the technology? Does it provide any sort of error console that might be logging issues?
As far as audio goes, it probably depends on the app and the context that it creates. My assumption would be that it is probably a shell around a WebView on iOS, and in that case it can make certain choices in how it wants audio to play, such as disabling autoplay. If you have a button that when tapped is set to play audio, does that work?
It might also be useful to see a zip of your .hype document and the export along with Coverage files.