Concurrent user limitation

I’m new at jitsi meet, I’ve just installed and config jitsi meet with jicocfo on ubuntu 18.04.
the main problem is, when I invite 3rd person in the meeting all of users are muted and camera didnt work. but it just works with only 2 users.
is there any limitation or special config for that?
any help will be appreciated
thnx in advance

Follow, this is normally a problem with firewall, port forwarding or not configuring jvb with the private and public address.