ModuleNotFoundError: No module named 'jupyter_server'

[伊藤泰輔]

I have 3 PCs and Windows Anaconda, but when I install Anaconda3-2020.07-Windows-x86_64.exe on one of them, I get an error when starting Jupyterlab.

The installation of Tensorflow also doesn't work. The other two are normal. 

Why is this happening?

I Pasted the error. If anyone knows, please let me know.

-------------------------------------------------------------------------------------------------------------------

Traceback (most recent call last):

  File "C:\Users\TaisukeIto\Anaconda3\Lib\site-packages\jupyterlab_server\server.py", line 20, in <module>

    from notebook.notebookapp import aliases, flags, NotebookApp as ServerApp

  File "C:\Users\TaisukeIto\Anaconda3\Lib\site-packages\notebook\notebookapp.py", line 49, in <module>

    from zmq.eventloop import ioloop

  File "C:\Users\TaisukeIto\Anaconda3\Lib\site-packages\zmq\__init__.py", line 47, in <module>

    from zmq import backend

  File "C:\Users\TaisukeIto\Anaconda3\Lib\site-packages\zmq\backend\__init__.py", line 40, in <module>

    reraise(*exc_info)

  File "C:\Users\TaisukeIto\Anaconda3\Lib\site-packages\zmq\utils\sixcerpt.py", line 34, in reraise

    raise value

  File "C:\Users\TaisukeIto\Anaconda3\Lib\site-packages\zmq\backend\__init__.py", line 27, in <module>

    _ns = select_backend(first)

  File "C:\Users\TaisukeIto\Anaconda3\Lib\site-packages\zmq\backend\select.py", line 28, in select_backend

    mod = __import__(name, fromlist=public_api)

  File "C:\Users\TaisukeIto\Anaconda3\Lib\site-packages\zmq\backend\cython\__init__.py", line 6, in <module>

    from . import (constants, error, message, context,

ImportError: cannot import name 'constants' from 'zmq.backend.cython' (C:\Users\TaisukeIto\Anaconda3\Lib\site-packages\zmq\backend\cython\__init__.py)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

  File "C:\Users\TaisukeIto\anaconda3\envs\test3\Scripts\jupyter-lab-script.py", line 5, in <module>

    from jupyterlab.labapp import main

  File "C:\Users\TaisukeIto\Anaconda3\Lib\site-packages\jupyterlab\labapp.py", line 14, in <module>

    from jupyterlab_server import slugify, WORKSPACE_EXTENSION

  File "C:\Users\TaisukeIto\Anaconda3\Lib\site-packages\jupyterlab_server\__init__.py", line 4, in <module>

    from .app import LabServerApp

  File "C:\Users\TaisukeIto\Anaconda3\Lib\site-packages\jupyterlab_server\app.py", line 9, in <module>

    from .server import ServerApp

  File "C:\Users\TaisukeIto\Anaconda3\Lib\site-packages\jupyterlab_server\server.py", line 26, in <module>

    from jupyter_server.base.handlers import (                          # noqa

ModuleNotFoundError: No module named 'jupyter_server'