Question: I can run jupyter notebook, but when I try to open a jupyter file I get the following error on my browser 500 : Internal Server Error in the console, I get this error message  To access the notebook, open this file in a browser: file:///C:/Users/Bruno/AppData/Roaming/jupyter/runtime/nbserver-23164-open.html Or copy and paste one of these URLs: http://localhost:8888/?token=1e5a289e6fd9b36cab176131f1e3d0b673921c1a76258552 or http://127.0.0.1:8888/?token=1e5a289e6fd9b36cab176131f1e3d0b673921c1a76258552 [W 16:19:04.850 NotebookApp] 404 GET /ipyparallel/clusters?_=1649168344196 (::1) 16.95ms referer=http://localhost:8888/tree [E 16:19:24.938 NotebookApp] Uncaught exception GET /notebooks/examples/jupyter_notebooks/greenhouse.ipynb (::1) HTTPServerRequest(protocol='http', host='localhost:8888', method='GET', uri='/notebooks/examples/jupyter_notebooks/greenhouse.ipynb', version='HTTP/1.1', remote_ip='::1') Traceback (most recent call last): File "c:\users\...\tornado\web.py", line 1697, in _execute result = method(*self.path_args, **self.path_kwargs) File "c:\users\..\tornado\web.py", line 3174, in wrapper return method(self, *args, **kwargs) File "c:\users\..\notebook\notebook\handlers.py", line 96, in get get_frontend_exporters=get_frontend_exporters File "c:\users\..\notebook\base\handlers.py", line 507, in render_template return template.render(**ns) File "c:\users\...\jinja2\asyncsupport.py", line 76, in render return original_render(self, *args, **kwargs) File "c:\users\...\jinja2\environment.py", line 1008, in render return self.environment.handle_exception(exc_info, True) File "c:\users\...\jinja2\environment.py", line 780, in handle_exception reraise(exc_type, exc_value, tb) File "c:\users\...\jinja2\_compat.py", line 37, in reraise raise value.with_traceback(tb) File "c:\users\...\notebook\templates\notebook.html", line 1, in top-level template code {% extends "page.html" %} File "c:\users\...\notebook\templates\page.html", line 154, in top-level template code {% block header %} File "c:\users\...\notebook\templates\notebook.html", line 114, in block "header" {% for exporter in get_frontend_exporters() %} File "c:\users\...\notebook\notebook\handlers.py", line 19, in get_frontend_exporters from nbconvert.exporters.base import get_export_names, get_exporter File "c:\users\...\nbconvert\__init__.py", line 4, in <module> from .exporters import * File "c:\users\...\nbconvert\exporters\__init__.py", line 4, in <module> from .slides import SlidesExporter File "c:\users\...\nbconvert\exporters\slides.py", line 12, in <module> from ..preprocessors.base import Preprocessor File "c:\users\...\nbconvert\preprocessors\__init__.py", line 10, in <module> from .execute import ExecutePreprocessor File "c:\users\...\nbconvert\preprocessors\execute.py", line 8, in <module> from nbclient import NotebookClient, execute as _execute File "c:\users\...\nbclient\__init__.py", line 6, in <module> from .client import NotebookClient, execute # noqa: F401 File "c:\users\...\nbclient\client.py", line 18, in <module> from traitlets import ( ImportError: cannot import name 'Callable' from 'traitlets' (c:\users\...\traitlets\__init__.py) [E 16:19:24.954 NotebookApp] { "Host": "localhost:8888", "Connection": "keep-alive", "Sec-Ch-Ua": "\" Not A;Brand\";v=\"99\", \"Chromium\";v=\"99\", \"Google Chrome\";v=\"99\"", "Sec-Ch-Ua-Mobile": "?0", "Sec-Ch-Ua-Platform": "\"Windows\"", "Upgrade-Insecure-Requests": "1", "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.84 Safari/537.36", "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9", "Sec-Fetch-Site": "same-origin", "Sec-Fetch-Mode": "navigate", "Sec-Fetch-User": "?1", "Sec-Fetch-Dest": "document", "Referer": "http://localhost:8888/tree/examples/jupyter_notebooks", "Accept-Encoding": "gzip, deflate, br", "Accept-Language": "es-MX,es;q=0.9,en-US;q=0.8,en;q=0.7,es-419;q=0.6,de;q=0.5,it;q=0.4", "Cookie": "_xsrf=2|d1d886ef|7780482558d83a8cceac4628e4649561|1649085007; username-localhost-8888=\"2|1:0|10:1649168343|23:username-localhost-8888|44:MTBiMWRjMTMzODlhNDUyM2IxYzMxNTgwZThlYTUyODk=|6f47252b3d75cbe3567f 0fb5380e2c6522193331  I am using Python 3.7 on windows and this is the list of packages I have installed absl-py==0.8.0 alabaster==0.7.12 appdirs==1.4.3 astor==0.8.0 atomicwrites==1.3.0 attrs==19.1.0 Babel==2.9.0 backcall==0.1.0 bleach==3.1.0 bokeh==2.3.1 build==0.3.1.post1 cachetools==4.2.1 certifi==2020.12.5 chardet==4.0.0 charset-normalizer==2.0.12 colorama==0.4.4 coverage==4.5.4 cycler==0.10.0 Cython==0.29.23 decorator==4.4.0 defusedxml==0.6.0 depinfo==1.5.1 docutils==0.16 entrypoints==0.3 fastjsonschema==2.15.3 future==0.17.1 gast==0.3.1 google-pasta==0.2.0 gpflow==1.5.0 gpytorch==1.4.2 grpcio==1.37.0 h5py==2.10.0 idna==2.10 imagesize==1.2.0 importlib-metadata==4.11.3 ipykernel==5.1.3 ipyparallel==8.2.1 ipython==7.10.2 ipython-genutils==0.2.0 ipywidgets==7.5.1 jedi==0.15.1 Jinja2==2.10.1 joblib==0.14.0 jsonschema==3.2.0 jupyter==1.0.0 jupyter-client==6.2.0 jupyter-console==6.4.0 jupyter-core==4.7.1 jupyterlab-pygments==0.1.2 Keras-Applications==1.0.8 Keras-Preprocessing==1.1.0 kiwisolver==1.1.0 latexcodec==2.0.1 Markdown==3.1.1 MarkupSafe==1.1.1 matplotlib==3.1.1 matplotlib-inline==0.1.3 mistune==0.8.4 more-itertools==7.2.0 mpmath==1.1.0 multipledispatch==0.6.0 nbclient==0.5.11 nbconvert==6.0.7 nbformat==5.3.0 nest-asyncio==1.5.1 nose==1.3.7 notebook==6.0.2 numpy==1.17.1 oauthlib==3.1.0 optlang==1.4.4 packaging==19.1 pandas==1.1.0 pandocfilters==1.4.2 parso==0.5.2 pep517==0.10.0 pexpect==4.7.0 phantomjs-binary==2.1.3 pickleshare==0.7.5 Pillow==8.2.0 Pint==0.10.1 pipdeptree==0.13.2 pluggy==0.13.0 ply==3.11 prettytable==0.7.2 prometheus-client==0.7.1 prompt-toolkit==2.0.10 protobuf==3.9.1 psutil==5.9.0 PTable==0.9.2 ptyprocess==0.6.0 py==1.8.0 pyasn1==0.4.8 pyasn1-modules==0.2.8 pybtex==0.24.0 pybtex-docutils==1.0.0 Pygments==2.5.2 pyparsing==2.4.2 PyQt5==5.13.2 PyQt5-sip==12.7.0 pyrsistent==0.15.6 pytest==5.1.2 python-dateutil==2.8.0 python-libsbml-experimental==5.18.0 pytz==2019.2 PyUtilib==5.7.3 pywin32==303 pywinpty==2.0.5 PyYAML==5.1.2 pyzmq==18.1.1 qtconsole==4.6.0 requests==2.27.1 rsa==4.7.2 ruamel.yaml==0.16.5 ruamel.yaml.clib==0.1.2 scikit-learn==0.21.3 scipy==1.3.1 seaborn==0.9.0 selenium==3.141.0 Send2Trash==1.5.0 six==1.12.0 snowballstemmer==2.1.0 Sphinx==4.5.0 sphinxcontrib-applehelp==1.0.2 sphinxcontrib-devhelp==1.0.2 sphinxcontrib-htmlhelp==2.0.0 sphinxcontrib-jsmath==1.0.1 sphinxcontrib-qthelp==1.0.3 sphinxcontrib-serializinghtml==1.1.5 swiglpk==4.65.0 sympy==1.4 tabulate==0.8.6 tensorboard==1.14.0 tensorboard-plugin-wit==1.8.0 tensorflow==1.14.0 tensorflow-estimator==1.14.0 termcolor==1.1.0 terminado==0.8.3 terminaltables==3.1.0 testpath==0.4.4 toml==0.10.2 torch==1.8.1 torchaudio==0.8.1 tornado==6.0.3 tqdm==4.64.0 traitlets==4.3.3 typing-extensions==3.7.4.3 urllib3==1.25.7 wcwidth==0.1.7 webencodings==0.5.1 Werkzeug==0.15.6 widgetsnbextension==3.5.1 wrapt==1.11.2 xlrd==1.2.0 zipp==0.6.0  The following is not related to the question above! I don't have any more details to write, but if I don't write something Stackoverflow complains that I am writing only code and doesn't let me post my message. So I am writing some more stuff to get to the point that he lets me post it. I find this check a bit annoing

Answer: The problem was solved by installing traitlets v5.1.1 and traitlets-widget v5.5.0