I have several remote Cisco 504g phones remotely connected (STUN) to my 3CX (version 14) that have been working flawlessly for more than a year. On Monday, they all lost ability to make and receive calls. I can provision the phones (factory reset and re-provision) and they appear in the 3CX phone list, but they "timeout" when trying to call any internal or external phone number. Our phones on the local network are not affected and are working fine. There were no known changes to any of the phones, no changes to 3CX, no OS server updates (Windows Server 2012), and the firewall was not changed either. The firewall on the server is disabled. I am quite baffled. Has anyone seen anything like this before.