Jupyter Notebook, missing toolbar with nbextensions

I'm using Ubuntu 20.04 and working in a virtual environment set up with pipenv. (Python version is 3.8) I like Jupyter Notebook and decided to install the package nbextensions. Installation finished without errors, I can activate a particular extension via the command line, but when I start Jupyter Notebook I don't get a toolbar on the start page where I can just put checks on the extensions that I want to enable.

I found this question posted here: https://stackoverflow.com/questions/49647705/jupyter-nbextensions-does-not-appear and read through it, but the solutions there do not help in my case.

Here is what I did:
(in a normal terminal where I have the virtual environment set up):

$ pipenv install jupyter_contrib_nbextensions
$ pipenv install jupyter-nbextensions-configurator

(both commands seem to be successful)
Then after activation of the virtual environment (pipenv shell) I run

$ jupyter contrib nbextension install --user
$ jupyter nbextensions_configurator enable --user

Those also seem to be successful.
I was able to enable the highlighting of a selected word by running jupyter nbextension enable highlight_selected_word/main. I tested it in a notebook and it works as it should, but it would be good to have the toolbar.
I tried jupyter nbextension enable nbextensions_configurator/tree_tab/main and got the following output:

Enabling notebook extension nbextensions_configurator/tree_tab/main...
      - Validating: problems found:
        - require?  X nbextensions_configurator/tree_tab/main

Here is the output of jupyter nbextension list (that I think looks suspicious):

Known nbextensions:
  config dir: /home/my_user_name/.local/share/virtualenvs/analysis-vLcf5S6s/etc/jupyter/nbconfig
    notebook section
      nbextensions_configurator/config_menu/main  enabled 
      - Validating: problems found:
        - require?  X nbextensions_configurator/config_menu/main
      jupyter-js-widgets/extension  enabled 
      - Validating: OK
    tree section
      nbextensions_configurator/tree_tab/main  enabled 
      - Validating: problems found:
        - require?  X nbextensions_configurator/tree_tab/main
  config dir: /home/vasil/.jupyter/nbconfig
    notebook section
      nbextensions_configurator/config_menu/main  enabled 
      - Validating: problems found:
        - require?  X nbextensions_configurator/config_menu/main
      contrib_nbextensions_help_item/main  enabled 
      - Validating: OK
      varInspector/main  enabled 
      - Validating: OK
      highlight_selected_word  enabled 
      - Validating: problems found:
        - require?  X highlight_selected_word
      highlight_selected_word/main  enabled 
      - Validating: OK
      nbextensions_configurator/tree_tab/main  enabled 
      - Validating: problems found:
        - require?  X nbextensions_configurator/tree_tab/main
    tree section
      nbextensions_configurator/tree_tab/main  enabled 
      - Validating: problems found:
        - require?  X nbextensions_configurator/tree_tab/main
  config dir: /usr/local/etc/jupyter/nbconfig
    notebook section
      jupyter-js-widgets/extension  enabled 
      - Validating: OK

Any ideas?

Hey I entered the same link you provided because I was having the same issue using Ubuntu 2204 into WSL. The second answer about downgrading to version 6.1.5 worked for me!

After downgrading ran jupyter contrib nbextension install --user once again, entered jupyter notebook, and done!