Failed to connect to ESP8266: Timed out waiting for packet header

[RealCorax]

Hi,
Im trying to follow the instructions from 'Everything Smart Home' https://www.youtube.com/watch?v=xS9KIWJJa_U
Ive connected the Zigbee device exactly as he mentioned as far as I can see. I have a solid green light on the Zigbee hub and a red light on the adapter.
When I run the Tasmotizer however, I receive the above error.
It 100% completes the Download section, and I can see on the adapter a small green light flashing.
However when it shows 'connecting' status it sits for about 15secs or so then i get this error.

Any help on this would be much appreciated please.