Jupyter notebook process freezes on startup

[kspeeckaert]

I'm using Jupyter on several platforms, but for some reason, I can no longer get it to start on Windows 10 (where it was previously working).

Starting jupyter notebook with the --debug flag, returns the following information:

The output freezes at that point, no browser is started and tried to open http://localhost:8888 returns no response. The process also does not react to CTRL-C, it has to be killed.

I've tried the following:

• regenerated (overwritten) the config file with the default settings.
• completely re-installed Python and jupyter libraries.
• tried starting jupyter notebook, jupyter lab and jupyter-notebook.

Looking at the process list, I can see jupyter-notebook.exe and associated process are started.

I can also see that the child python.exe process is listening on port 8888.

The output for jupyter troubleshoot is available here (too exhaustive to paste).

Any help or pointers would be greatly appreciated. Short of debugging it using pdb, which was suggested on Stack Overflow, I don't really know what else I can do/try.

[kspeeckaert]

I compared the output to a working environment, and found that after the point where it freezes, jupyter normally loads the extensions. So I performed the following command:

jupyter nbextension list

which returns:

Known nbextensions:
  config dir: c:\dev\venv\jupyter\etc\jupyter\nbconfig
    notebook section
      jupyter-js-widgets/extension enabled
      - Validating: ok

I then tried to disable the extension using jupyter nbextension disable jupyter-js-widgets.

Running jupyter nbextension list again now results in the following output:

Known nbextensions:
  config dir: C:\Users\Admin\.jupyter\nbconfig
    notebook section
      jupyter-js-widgets disabled
  config dir: c:\dev\venv\jupyter\etc\jupyter\nbconfig
    notebook section
      jupyter-js-widgets/extension enabled
      - Validating: ok

Jupyter notebook now works again, but I don't know yet what the impact is of having to disable the extension or why it certainly became an issue.