See the VoxATC manual pages 82-83. Make sure firewall settings are correct. I got it to work (v7.41)... but was having problems with the voice configuration on the server. A windows issue I think. I haven't been back to resolve that. But it otherwise connected and appeared to be working (minus voices).
I received this email from Tegwyn back in October. I think others have had more recent responses from him. Knowing how software development goes... I'm waiting patiently. I know He'll come through for us. Hello We are working on a new version of VoxATC that will work with P3D V3. But release is a couple of months away. Regards Tegwyn West