Hi there,
There are many different things that could cause this problem. It could be a failure in sink initialization, failure to serve the web page with proper CORS headers, failures to load the asset bundles containing the banks and media, or simply the web browser defaulting to a muted state.
Are there any errors popping up in the Console Log tab of the Dev Tools pane in Chrome? Usually, this is where you would see any errors generated by Wwise.
If nothing shows up there, you may want to try connecting the Wwise Profiler and see if the sound engine is actually processing audio events. Note that to connect the profiler to a web page, you will need to use the proxy server that ships with the Wwise SDK; please make sure to consult the offline documentation for the Experimental Web Platform.