Hey @Stewart1
We are using ULAW for the calls. When we ran tcpdump on FreePBX and on phone, what we saw is FreePBX was hearing the audio from PSTN just fine, but nothing from the phone. The phone itself was recording that it was sending audio out (towards the PBX) but no inbound audio.
We could hear ringing as the call was being setup and progressing, but once the remote party picks up it goes dead for both ends (neither can hear the other).
As I mentioned above, I did just install Tailscale on Freepbx just now, and in testing it is working with phones pointed at the tailscale IP versus the internal LAN IP of FreePBX. I don’t really want to leave it this way (tailscale client behind another tailscale client) but it is hopefully a clue as to whats going on.
Thanks,