Hello, System: 3CX v15 Gateway: Patton SN4112 (1 line only) Phones: 40 x Yealink T42G Switch: HP 1920-48G PoE Router: Drayek 2860 Currently if anybody rings in via the analog BT PSTN, the call is routed to one specific extension. Everything has been working fine for a few weeks, all calls have successfully been dialing in on the extension configured as inbound (20 - 30 calls per day). Everybody is able to also ring out via configured dialplan (dial 9 before number). As of yesterday, external calls aren't going through to the extension anymore. The call log shows the calls coming in onto the extension but the last 'Talking' column just shows 'Not Answered'. I'm ringing in right now via my mobile to test and the IP phone is just not ringing. The Patton gateway shows the FXO LED blink whilst I ring in so the call seems to be coming in. Everybody is able to ring out successfully so it's just the incoming call. I've so far tried changing the inbound to a different extension but this hasn't worked. Nothing has been messed around with at the site (server room is under lock and key). Network is fully operational, the Patton is showing a successful link to the PBX. How can I start to try and diagnose this? Has anybody else had a similar issue where the inbound calls just stop routing in out of the blue? Any help is appreciated.