It has been awhile since I have been in the code but, does the webserver logic still expect two video streams before enabling the video? Look at the logic of how each video element is setup and how many expected video streams are recognized. app.js and video-player.js look at them both.
The other thing I did was disabled the Camera, CameraStreamer and AudioStreamer components on the “Render Streaming Camera 2” game object, but left the Simple Camera Controller component enabled (the RenderStreaming script seems to need a camera controller for each browser client).