You'll love this. I tried every NAT combination (our firewall doesn't like anything but itself maintaining NAT control). I tried changing the Auto/Native/NAT settings. Nothing worked. All programmable settings for the softphone and endpoint were identical to other endpoints on the system. I copied all settings from a random endpoint and copied them to the softphone and endpoint connected by WAN. Voila! They worked. There was something, not available in the programming, that wasn't working. Go figure.