I have two Polycom units. An HDX 7000 and an older model. I can connect to Polycom test IPs just fine but when I try to connect with our sister company's Polycom it doesn't work. After making connection they can see and hear me but I can't see or hear them. They can connect to the Polycom test IPs as well without issue. I have an older Polycom unit at our main location and I can't connect to our sister company at all. I've verified the firewall ports a thousand times and they are correct.
Is there something I should be looking at specifically?
If you cannot see the return traffic, you are stopping it on a firewall or not forwarding the ports to the internal IP - hence they can see you.
Do you have NAT enabled? Are you sending the NAT address to the far end or the private address?