The GSM gateway (Yeastar TG400) currently refuses to register with my Grandstream UCM6308, so calls never make it through. I have remote access to both devices ready for you and can open the ports you need. I have not yet verified every network or SIP setting, so the first step will be a thorough review of both sides—IP addresses, SIP trunks, codecs, NAT, authentication and routing rules—until the two units establish and keep a clean connection. Once registration is solid, I want unanswered calls to be diverted automatically after 30 seconds. Set up and test the forwarding rule so an incoming GSM call that rings for half a minute is routed to the specified fallback destination without fail. Deliverables • Stable TG400 ⇄ UCM6308 SIP registration • Working 30-second no-answer forwarding, fully tested on live calls • A short note listing the key settings you changed so I can maintain them later If this sounds straightforward to you, let’s get it done today.