Why doesn't webrtc audio only work?

Question

JavaScript

I tried different libraries to implement voice transmission between two clients, none of them transmit sound. Tried different browsers, OS, etc. Doesn't work anywhere.
Even this example https://simplewebrtc.com/audio.html?test123
does not work, we go there with a person, we appear in the room, but we do not hear each other.
What is the problem?