Lost connection to GitHub Repo

I am getting error:

Failed for the root '"https://github.com/xxxxx/xxxx#refs/heads/main" {instance id=2, parent internal id=1, parent id=xxxxx_HttpsGithubComxxxxyyyRefsHeadsMain, description: "https://github.com/xxxxx/xxxx#refs/heads/main"}: git -c core.askpass=C:\TeamCity\temp\pass13164680956937501901.bat -c credential.helper= ls-remote origin command failed. exit code: 128 stderr: fatal: 'origin' does not appear to be a git repository fatal: Could not read from remote repository. Please make sure you have the correct access rights and the repository exists.

This suddenly started yesterday, typically after a critical bug was found which I need to deploy.  I've been scratching my head all weekend... and googling, a lot.  Aside from a couple of minor software version bumps I hadn't changed any config for a very long time, it has just been working, until now. 

It looks to me like the passnnnnnn.bat file it is talking about is not being created.

I am:
 ● Running Team city server (and agent) in a windows docker container on Windows 11 using the jetbrains image from dockerhub hosted by Docker Desktop with the build in DB.
 ● Trying to access a private repo (non-enterprise).

I have:
 ● Checked that the url is correct (a lot of times!!).
 ● Rolled back a recent update of teamcity from 2022.10.3 to 2022.10.2 - which I believe is the previous working version that I was using.
 ● Rolled back a recent update of docker desktop from 4.18.0 to 4.12.0 - which I believe is the previous working version that I was using.
 ● Tried on another machine with fresh setup of docker container pointing to a copy of teamcity volumes from my primary machine.
 ● Cleared git cache (by deleting comtents of data\system\caches\git and also from 
 ● Restored from a known working teamcity backup from December 2022.
 ● Created a new VCS root, with newly generated personal access token (both classic and fine grained) 
 ● Created a new TeamCity authorised OAuth App in Github.
 ● I even tried using GitLab as a repository source.

The error stubbornly won't go away and I can't do very much at all!  Please help, I am out of ideas.