Camera and sound problems when adding a new participant in a jitsi meeting

Hello Everyone

I have installed Jitsi on my own server and I still have problems. when it is running between only 2 persons, everything is going OK, but when the 3rd participant shows up, it seems like his camera and micro are closed.
We can not either see him or listen to him.
Can you please provide me any solution or figuring out where exactly is the problem?

Thank you in advance