I am stumped as my DID provider can't route via SIP URI to PBXes but they can to IPTel. I can call my own PBX, and from my own PBX to the PBXes URI without issue. When I route the DID via URI to IPTel and set voicebox it works and routes to the voicebox. When I add a forward for the PBXes URI it then breaks and gets a denial of 404 not in service.

Ideas anyone? I am scratching my head here. Appreciate any help!