You only see the first two people who join the conference

When 2 people participate in the conference, everything works correctly, but if there are 3 people, only 2 are seen. The third person does not get the video. I have to configure something?

We have our own jitisi-meet server installed.

This normally is a problem of not forwarding the ports or not configuring jvb public and private addresses. https://github.com/jitsi/jitsi-meet/blob/master/doc/quick-install.md#advanced-configuration

This has something to do with being in a cloud vps ?

Yep, normally cloud VPS run machines behind nat and firewalls are configured not on the machine but some outside web console.

Ok, I’m going to open ports 10000-20000 / udp in the provider’s firewall. Need another than the 80 and 443?

You just need udp 10000, 80 and 443.
Is your machine behind NAT? If you execute ifconfig do you see the public address of the machine to be configured to a local interface?

only with opening the ports in the supplier’s firewall and everything seems to work fine.
Thank you so much for everything