This appeared to be a Tasmota firmware issue. I upgraded it today using the online OTA upgrade and repeated exactly the same steps as before. It worked.
For what it’s worth (and this is just observational and not coming from any expertise. It may just be that I’m naive about what changed) the fix contradicted much of the advice that already exists. Downloading the two main firmware versions in the guides didn’t work. It was only when trying to use the firmware directly from the tasmota site via the OTA upgrade option, that I got it to work with ZHA.
Secondly, it still refused to work with Zigbee2mqtt. Herdsman (in the logs) would say it couldn’t open a socket. Guides say you need to use module 75 for z2m but I got it working when I switched back to module 0, intended for ZHA. I don’t understand why, but it works like a charm now in both ZHA and z2m.
This may help others out but I accidently did the normal Over the Air Firmware upgrade of Tasmota which broke mine. The log would attempt to start TCPStart on port 8888 but an “unknown” error would come back.
My fix was to run the following command to reflash it with the correct OTA firmware:
Console Command to set new OTA path: otaurl http://ota.tasmota.com/tasmota/tasmota-zbbridge.bin.gz
Then In the firmware menu, I ran the OTA. The process seems to do a minimal firmware install first up, so give it a couple of minues to do its thing. Check your console and hopefully that TCPstart has launched now that the command is actually in the firmware.
I have spent several days to solve it. Just check in Configure template - Name “Sonoff zigbee Pro” if you have GPIO 19 set to TCP TX and GPIO 23 to TCP RX and run the command in a console backlog rule1 on system#boot do TCPStart 8888 endon ; rule1 1 ; template {"NAME":"Sonoff Zigbee Pro","GPIO":[0,0,576,0,480,0,0,0,0,1,1,5792,0,0,0,5472,0,320,5793,5504,0,640,608,32,0,0,0,0,0,1,0,0,0,0,0,0],"FLAG":0,"BASE":1} ; module
Also I have the same issue with my Sonoff Bridge Pro and ZHA. After I had problems with Zigbee2MQTT (Home Assistant has often lose the connection), Because of that I have decided to try ZHA. I have exactly the same situation as @uSlackr
Is it really the only one solution to buy other (USB) Bridge?
Probably to late now, but I found a solution for my Sonoff Zigbee Bridge (not the pro version). After two days of trying all new versions of software and even a new Bridge, I went back to what digiblur did (How to use the Sonoff Zigbee Bridge with Home Assistant - Tasmota | digiblurDIY) and used the same ota file, nl ncp-uart-sw_6.7.6_115200.ota to uupgrade the firmware, and it worked seamlessly.
Just for information for those who still has problems…
After I realized my ZbBridge (not pro) stop work with HA I did several upgrades of Sonoff and finally it works on [Tasmota 14.3.0 (release-zbbridge) + ncp-uart-nsw_6.7.9_115200.ota
final problem was that port 8888 was not open because I did not activate it in TASMOTA menu-Configure Other - template