gitea ssh refuses to authenticate for one particular pc in the network

  docker, git, gitea, ssh, synology

I’ve got a docker image of gitea up and running on my Synology NAS, and it has been running fine for some time now. I could fetch, clone, pull and push with no problems. I also have 2 laptops at my home network.

The problem is that one of those laptops suddenly can’t fetch the repo over ssh (http works fine). The error is:

$ git fetch origin
FATAL ERROR: Network error: Connection refused
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

When I try to ssh -v to it, I got bunch of logs and this in between:

Hi there, <name>! You've successfully authenticated with the key named <my_mail>, but Gitea does not provide shell access.
If this is unexpected, please log in with password and setup Gitea under another user.

It looks like Gitea is accessible, but unable to process the request from this particular PC.

I tried to remove and re-add public auth key in gitea GUI but it didn’t help.

I also tried to execute following in Site Administration: Update the '.ssh/authorized_principals' file with Gitea SSH principals. and Update the '.ssh/authorized_keys' file with Gitea SSH keys. – didn’t help, either.

Gitea is NOT using build-in ssh.

This is SSH config part of Gitea configuration:
enter image description here

What could cause the problem? How can I attempt to fix it?

Source: Docker Questions