Thank you very much for the answers.
It is possible that I should have provided more network configuration first and provide more details about it.
The server IP address is → 104.200.73.227 which is a public IP address (cloud server) U.S.
Our phones are in Asia.
The SIP server IP address is → 190.119.245.139:5160, Peru
Media Server → 172.31.229.113
The central has two internet links and a VPN with a SIP provider, they use that mask to communicate with said provider, that IP is in the SIPNAT as the central’s external address.
The audio from the central is not heard because it is waiting for RTP from another IP, because we keep waiting and sending a response from another IP and that is why it is cut off after 8 seconds once the call is established.
Here is the PJSIP SET LOGGER ON