The SBC (raspberry PI 4) shows a green light in 3CX Management Console SIP Trunk area and appears to have had no issues in the install phase and is UP. Using a regular ethernet cable, your phone can be powered from a Power over Ethernet (PoE) compliant router or switch.

You need to begin with a PBX that has been deployed properly (meaning the firewall rule entry is removed manually, and recreated by PBX Express automatically) -> This is one variable eliminated It seems by having the SBC we have simply just shifted the network admin from GCP to the Office Cisco router, which is more complex and more problematic and expensive to troubleshoot. I followed through the instructions above. The Base reset Ok, and once the base reset the handset automatically said de-register the handset? on the screen, so i pressed yes. The set of instructions thereafter to deregister the handset therefore could not be followed to de-register the handset as described as it had already de-registered itself and said so. It couldn't therefore do the handset reset. So I then added the provisioning URL for Local LAN (in the office), not SBC remote, which i had used before, seeing that makes more logical sense given we now have the SBC, as the provisioning method. Having confirmed and pressed the auto-provision button, the Web Gui says Operation Completed, but the handset then said Unregistered.

So until we forwarded the incoming port 5001 on our LAN to the SBC, the W60B phone could not auto-provision and that seems perfectly logical given the above. If you don't yet have a base station, follow these steps. If you are adding an additional handset to an existing setup, go to Assembling the Phone.

Once the handset displays the time and handset number, it is connected. To test that it's connected, press the Hands Free Speak button. If you hear dial tone, the phone is connected. Adding Handsets The PBX Express install onto GCP actually makes all IPs allowed for INGRES into the PBX via specific ports including 22,443, 5060, 5090 and 9000-10999 etc. the defaults. Designed in modern and elegant style, this compact DECT IP base station possesses a wire-hidden design, presenting a concise and tidy desk to you even being mounted to the wall. By supporting Opus codec, Yealink W60B consistently delivers excellent and profes- sional audio quality in both high-bandwidth and poor network conditions, comparing with other wideband or narrowband audio codecs.NOTE: If you are using Power over Ethernet (PoE), you don't need to connect the AC adapter. Make sure the Ethernet cable and router or switch is Power over Ethernet (PoE) compliant. ¶ Power over Ethernet (PoE) If there are multiple lines assigned to your handset as outgoing lines, press the Line soft key to select the desired line. If a line is not selected, the handset uses the default outgoing line to dial out. I would be most grateful for your help as I have no way to diagnose where it's going wrong and have spent hours on this problem. I can't tell if the issue of registering is happening at the LAN side or the PBX side, and there seems to be no definitive document from 3CX to say what ports where must be open for the SBC on a LAN behind a firewall to work with remote phones. Press ▲ or ▼ to highlight the desired forwarding type (Always, Busy or No Answer) and then press the OK soft key. Both BT Cloud Voice and BT Cloud Phone portals include facilities to add or delete new devices (licences) and no doubt there is an assumption someone is actively managing them. The issue may arise though on SME with a small number of lines, sending out preconfigured kit and people simply using the pre-setup or express setup.

Features -> General Information -> Number Of Active Handsets --> Set to 8 (if you have more than 4 handsets) If you need help then our team are available from Monday to Thursday (between 9:00am and 5:30pm GMT) and on Friday (between 9:00am and 4:30pm GMT) Video tutorial explaining Auto Provisioning setup for Yealink Phone on PBXware 5. ¶ Requirements ¶ Identifying phone model You can enable/disable DND via the handset for each of the SIP accounts allocated to the Yealink handset: Only once the above is done should you then pair the handsets with the base, not before. And I can promise you that it will begin to work like a charm (having set one up myself yesterday behind a corporate firewall and on an SBC on the same network as the W60B base).In most cases if businesses change their equipment or move their service to a new provider it will initiate a change however if a business simply ceases (BT’s risk) or the kit is stolen there may be an issue (customers risk). BT owned equipment should be returned and yes BT really should clearly label their kit and their process however they should also ensure that equipment cannot simply be acquired and used on a customers account. I think @cobaltit was correct in saying you are overthinking it and in your honest attempt to get it to work you appear to be introducing variables instead of eliminating them, so how about we start from scratch with a clean slate?