We are a new paid 3cx customer and cannot get the Firewall Checker to pass. SIP vendor (Time Warner) is coming tomorrow. The firewall is a Sonicwall NSA 2600, firmware 184.108.40.206-12n Enhanced. While not an expert, I know Sonicwall and have been using them for years. We have followed 3cx's (http://www.3cx.com/blog/voip-howto/sonicwall-firewall-configuration/) guidance to the letter and double and triple checked. Our 3cx vendor says everything is set up correctly. The fix mentioned here: http://www.3cx.com/blog/voip-howto/sonicwall-important-update/ should not apply as we are on a much later firmware. The Firewall and NAT policies are setup per the above and the 3cx system is using the same external ip as the Sonicwall WAN interface. I tried changing the 3cx public ip (via dns) to another of our static ips but that did not work either. The message we receive is: No response received or port mapping is closed. However, I have confirmed that the port forward is working correctly as I am able to browse to the 3cx Server Manager on port 5000 (one of the forwarded ports) from an external computer. As all ports are in a service group (per the above guidance), if 5000 is working then the rest are working. I have also confirmed that port forwarding is working for other services (e.g. terminal services). The firewall on the Server Manager machine (win 8.1) is off. We purchased support from 3cx (in addition to support from our vendor) and 3cx support punted and said talk to the network admin (me) or to sonicwall. Not sure what Sonicwall can do as port forwarding is working .. Help! Please!