FIXED!!!

The login & sessionId sides of the script needs updating as below, which is based on Mike's older version, but it worked for me :)

(Only applicable if your still using MikeF's original V6 script.)

#!/bin/bash
# Sends current and target temperatures to Domoticz

cd "${0%/*}"

login ...

OK, I'm making progress. By using Stream (an iOS network debug tool) to sniff the protocol from the iOS Hive app, I've found that it calls

https://beekeeper-uk.hivehome.com/1.0/cognito/refresh-token

passing it a token, accessToken and refreshToken

It gets the same items back with new values, and ...

My script failed a couple of hours ago. Now when I try to get a session from
https://api.prod.bgchprod.info/omnia/auth/sessions
I get
{
"genericError": {
"error": {
"reason": "GONE",
"message": "Not supported anymore"
}
}
}

I can get an OAuth Bearer Token, using the Authorize button at
https ...