If your Teampel Server is installed in a LAN environment and users are connecting to the Teampel Server via Port Forwarding, there might be a lost of audio when making a voice call; or if your Teampel Server is installed on AWS or GCP these type of cloud servers and you are experiencing a muted voice call with the embedded SIP VoIP service, please see below solution:
Please first make sure TCP/UDP 35004, UDP 35100~40000 ports are opened on your router under port forwarding (for details on port settings: Which ports of my firewall need to be opened?).
If Solution 1 did not solve the problem, delete the NAT setting in Solution 1 and try Solution 2.
Solution 2 (For users using 3rd party SIP server):