Everything goes fine until I get to the part where I flash the zigbee module. I perform the firmware upgrade procedure using the required .ota file (in this case version 6.7.9, though I have tried multiple) but the upgrade gets stuck at “Upload Transfer” and goes no further than this. In the console output I see:
18:22:26.102 UPL: Transfer 192240 bytes
18:22:26.102 UPL: Successful 192240 bytes
18:22:26.114 HTP: Upload transfer
But it gets stuck there and goes no further. I have rebooted and redownloaded the files many times and used different client machines but nothing seems to work. Does anyone know what I am doing wrong?
I actually found the solution to this in the end. I had to flash an earlier version of Tasmota first, and then it would let me flash the Zigbee module (I used an earlier version of ota file for that as well, just to be safe), then I was able to upgrade both to latest. It seems to break things if you install the latest version of Tasmota over stock Sonoff firmware for some reason.