title: How to handle Jupyter Notebook NBextension config error?
body: <p>I installed nbextension to my Jupyter Notebook. But when I was using large datasets it made a big slow down. Then I removed NBExtension but after uninstallation, 500 Internal Server error started. Now I tried to reinstall Anaconda but the problem is still there. </p>
  
  <pre><code>     nbextensions_configurator/config_menu/main enabled
    - Validating: problems found:
      - require?  X nbextensions_configurator/config_menu/main
    contrib_nbextensions_help_item/main enabled
    - Validating: ok
    hinterland/hinterland enabled
    - Validating: ok
    autosavetime/main enabled
    - Validating: ok
    select_keymap/main enabled
    - Validating: ok
    jupyter-js-widgets/extension disabled
  tree section
    nbextensions_configurator/tree_tab/main enabled
    - Validating: problems found:
      - require?  X nbextensions_configurator/tree_tab/main
  edit section
    ruler/edit enabled
    - Validating: ok
    codefolding/edit enabled
    - Validating: ok
  config dir: C:\ProgramData\Anaconda3\etc\jupyter\nbconfig
  notebook section
    jupyter-js-widgets/extension enabled
    - Validating: ok
    nbextensions_configurator/config_menu/main enabled
    - Validating: problems found:
      - require?  X nbextensions_configurator/config_menu/main
  tree section
    nbextensions_configurator/tree_tab/main enabled
    - Validating: problems found:
      - require?  X nbextensions_configurator/tree_tab/main
  config dir: C:\ProgramData\jupyter\nbconfig
  notebook section
    nbextensions_configurator/config_menu/main enabled
    - Validating: problems found:
      - require?  X nbextensions_configurator/config_menu/main
  tree section
    nbextensions_configurator/tree_tab/main enabled
    - Validating: problems found:
      - require?  X nbextensions_configurator/tree_tab/main
  </code></pre>