Jupyter notebook does not connect to custom kernel - Notebook - Jupyter Community Forum
A connection to the notebook server could not be established. The notebook will continue trying to reconnect. Check your network connection or notebook server configuration. · Issue #5577 · jupyter/notebook · GitHub
Messaging in Jupyter — jupyter_client 8.6.1 documentation
POST api/kernel return 'Kernel does not exist' · Issue #337 · jupyter-server/kernel_gateway · GitHub