For regular live and unrecorded WebRTC with H264 @Ketan Bhimani, we suggest Opus as the audio codec as you correctly show. But if you want to record that WebRTC stream, the Opus has to be transcoded to AAC for playback. The mp4 container will require AAC for that recorded stream to play the audio. That’s why your recorded stream won’t play audio.
Both your source stream and your transcoded stream with AAC audio will be recorded, but only the transcoded stream with the AAC will be usable.
Here is the doc that explains recording webrtc and the need to convert the audio to AAC for mp4 playback:
Hope that solves it for you. You’ll need to use the Engine transcoder to create a stream that’s recorded with AAC.