Yes @ssls6 but, it turned out that that is not enough. 🙂
It turns out that if you Mac is connected to two interfaces, one via WiFi and the other via Ethernet and WiFi and Ethernet are on tow different subnets the calls will not work even if the iPhone is on the same WiFi as the Mac.
All of the Mac network interfaces must be on the same subnet, and in my case they were on different ones. This prevented the phone calls. Once I disconnected the ethernet and left WiFi only everything worked.
At home I have ethernet (via thunderbolt display) and WiFi, but they are both on the same subnet. So it works. At the office they are on two different subnets and it did not work.