Participants can't connect to Conference

Hi. Im taking my frist Jisti steps and having issues all the time.

This is the matter:

Im trying to do is set up a local instance for learning so i install a local ubuntu virtual machine and im trying establish a conference between that virtual machine and the host machine. But they don’t seems to see each other. As you can see in the image below both machines are in the helloJitsi lobby but only one participant is displayed:

Any ideas?

Thanks on advance.