On incoming VOIP - We have audio On outgoing VOIP - We do not have Audio Firewall - 5060 UDP - Outbound 5060, 5061 TCP/UDP - Inbound 9000-9049 UDP - Inbound Also using a STATIC IP that is not 1-to1 NAT - but each inbound port is mapped from external traffic pointed to the Static IP to the pbx internal ip of 10.0.0.12 Run firewall checker: 3CX Firewall Checker, v1.0. Copyright (C) 3CX Ltd. All rights reserved. <13:53:37>: Phase 1, checking servers connection, please wait... <13:53:37>: Stun Checker service is reachable. Phase 1 check passed. <13:53:37>: Phase 2a, Check Port Forwarding to UDP SIP port, please wait... <13:53:41>: UDP SIP Port is set to 5060. NO RESPONSE received. Phase 2a check FAILED. Application exit code is -2 In my firewall, I see port 3478 is blocked when I try to run firewall checker. I do not see 3478 listed anywhere that I need to open.