When using cloud-based SIP providers, the “in-band audio call progress” feature must be enabled (“phone settings” tab of Viking IP Programming software).  If using VOIP.MS, outgoing calls will not work until the caller ID has been programmed in the VOIP.MS set-up.  On the VOIP.MS portal, go to “main menu”, “account settings” and then click on the “general” tab.  Enter a phone number in the “CallerID Number” field and apply the change.