Twilio Trunk / FreePBX / Can't Hear Other Party

So I have a Twilio trunk and when I call out from my Poylcom phone it rings, the other party answers but neither of us can hear each other.

If I look at the recording in the Twilio admin I can play them back and here that there is actually voice.

Any ideas what this could be? I am very new to setting this up and hope someone has seen this issue before with Twilio.

Thanks in advance.

In No Matching Endpoint - Best way to fix? , you said that it was all working.

Is this the same system?

If so, do you know what may have changed that caused it to stop?

If it’s a different system, explain what’s different.

Confirm that in Asterisk SIP Settings, External Address and Local Networks are correct (your public IP may have changed).

Do calls between extensions work correctly?

Does echo test (dial *43) from the Polycom work correctly?

Confirm that the recording at Twilio does contain voice from both parties.

  1. Yes this is the same system. We are not live with it so I am not sure what could have changed.

  2. Asterisk SIP settings for Network is confirmed correct.

  3. Yes calls between extensions do work correctly.

  4. The echo test does work.

  5. I have confirmed that the Twilio recording contains both parties.

Do incoming calls have the same issue?

Run tcpdump on the PBX and capture all packets from a failing call. Move the capture file to your PC and open it in Wireshark. Look at the incoming RTP, if any.

If there’s none, this seems like a simple networking issue. If it’s present and correctly formatted but silent, I’d open a ticket with Twilio. If it’s somehow ‘bad’, e.g. wrong codec or packet size, post details.

Also, describe your network setup (router/firewall make/model, ISP gateway, etc.)

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