Spawn failed: 404 client error for http+docker://localhost

I have created a setup, where I use a docker container where I start a lot of things (kafka, mongoDB etc…) with a docker compose file.

In the past months, this worked and I could access it in the browser via the IP.

Now I wanted to check out my backend again and I get following error when I want to start my server in jupyter hub.

spawn failed: 404 client error for http+docker://localhost/v1.41/images/create?tag=latest&fromimage=backend_jupyterlab: not found (“pull access denied for backend_jupyterlab, repository does not exist or may require ‘docker login’: denied: requested access to the resource is denied”)

the backend_jupyterlab is nothing more than this (Dockerfile):

FROM cschranz/gpu-jupyter:v1.4_cuda-11.2_ubuntu-20.04_python-only

RUN conda install --quiet --yes
&& conda clean -tipsy

Does anyone have an idea what the issue could be? This would be extremely helpful, since this implementation already worked (in July) and now it suddently doesnt anymore.