I'm able to call people from the phone and they can hear whatever I say, but I hear nothing whatsoever.
When I first pickup the phone I'm able to hear the dial tone and I can hear the numbers as they are being pressed so it isn't a problem with the handset.
I've checked to make sure there isn't anything setup for a headset or anything like that, but I can't figure out what the problem is.
Anybody have any ideas?
Edit: Found somebody else with a similar problem and it ended up being that the firewall was letting traffic out but not back in, which is why the other person could hear them, but they couldn't hear the others. Will update this once I take a look.
To the guy who asked why I would ask the forum...the answer is because it was likely related to an IT issue (i.e. a firewall issue).
What do you see when you go to
Menu→Status→Diagnostics→Media Statistics? (This is the path on a 430. It may be different on the 550.) Specifically, what does "Rx Packets" show? If it's zero then there is likely a network problem keeping RTP from making it back to your phone. If it's nonzero then there is likely some other problem.AFAIK, tone and DTMF are generated by the handset so they're not a valid test of network connectivity.
This is almost always related to firewalling. Keep in mind that both H.323 and SIP are very complex protocols. Data is sent as many separate channels.
If your network is also doing NAT you are going to have to either add a gatekeeper or proxy or update your endpoint configuration. Polycom devices do have a configuration option you can set to make them aware for a NAT.
If an endpoint doesn't have any configuration options to deal with NAT or limit the ports so you can allow them through the firewall then you will need to add a device to your network to make things work. On an H.323 network you need to setup a gatekeeper or application level proxy to get the traffic to work (I use gnugk). For SIP this is called the a session border controller.
For an IP video connection you will typically have at least the following separate connections. With the exception of the control channel any one of the other channels could be blocked by the packet filter and the call could remain open.