I went to your discourse link. As Lorenzo was trying to say, you will want to get a better idea what is going on with ICE candidate gathering. In firefox there is an about:config setting that might help with this:

  media.peerconnection.ice.obfuscate_host_addresses = false

which will show the actual deobfuscated candidates host addresses. Here is a tool you can run on your client to see the stun candidates received.

https://webrtc.github.io/samples/src/content/peerconnection/...

If you do not get any valid candidates, then it is most likely a misconfiguration of your browser, vpn, firewall or network. Unfortunately this is most likely not a Janus thing, but I would need more information to know for sure.