NotebookApp not being culled

[manics]

It’s a bit complicated

See this post

Which is the correct way to cull idle kernels and notebook?

While the two aim in general to solve the same category of problem (wasted resources), they have different metrics available and different levels of action to take. The notebook-environment configuration should in general produce better, more fine-grained results because it can do things like cull unused kernels and be aware of things like idle/busy or connected status. This lets the notebook server make more intelligent choices like “shutdown a kernel if it’s been idle for 5 minutes BUT not if…

and the follow-ups, especially about turning on debug logging and ServerApp vs NotebookApp.