First, You have to make sure service is running. To do it just go to Services /Configuration leaf in left VSM tree. In the upper part of window You can see label „Voip Switch Service status". Status should be "RUNNING".
If shown status is "STOPPED", you should press START button to start service. Status should change to "RUNNING", make sure service started properly. To do so go to "Services log" pane and make sure entry "Service started" is there (please make attention to set correct date in log filter).