I've got a Cisco SPA504G at a remote home office. We can make outbound calls from it, and can call other extensions at the office, with no difficulty. Nobody can call to it though. The 3CX Phone for Windows doesn't seem to connect in CTI mode either. One thing that I'm thinking may be an issue is that the user's home network looks like this: <Internet>---<Vonage Router for home phone>---<linksys wireless router>---<switch>---<phone> I'm wondering if the Vonage services uses the same port. What I found online is that it uses 5061, while the Cisco is set for 5060.