ESP32 MQTT onMessage Callback never called

Matching the sketch file to the JSON output list you show above and you do seem to be getting door state in Setup when getShadow() is called...
Requesting Shadow [$aws/things/chicken-door/shadow/name/door/get]: {"state":{"reported":{"value":"closed"}}}
But I cannot figure out where this (the bold bit) is coming from, it cannot be messageReceived() as this would start with Received [ if it did.

EDIT:
I still don't know where it arrives in the sketch but this outlines what and where the response is comming from for the /get.