3CX WebRTC Client ↔ 3CX Tunnel/SIP Proxy (Port 443/5001/5090).

This report is structured for IT administrators and technical support teams to diagnose and resolve the problem systematically. 1. Executive Summary Issue: A WebRTC (Web Real-Time Communication) client (e.g., Chrome/Edge browser, 3CX WebClient) fails to register its SIP line with the 3CX Phone System. The extension appears as "Unregistered" or "Red" in the Management Console, preventing inbound/outbound calls.