jupyter nbconvertでFileNotFoundErrorが出る

Question

前提・実現したいこと

コマンドライン上でipynbファイルを実行しようとして、
jupyter nbconvert --execute --inplace main3.ipynbを実行したら、
以下のエラーメッセージが発生しました。

発生している問題・エラーメッセージ

> jupyter nbconvert --execute --inplace main3.ipynb
[NbConvertApp] Converting notebook main3.ipynb to notebook
[NbConvertApp] ERROR | Failed to run command:
['C:\Users\username\anaconda3\envs\tf1\python.exe', '-m', 'ipykernel_launcher', '-f', 'C:\Users\username\AppData\Local\Temp\tmpo3vp9838.json', '--HistoryManager.hist_file=:memory:']
    PATH='C:\Users\username\anaconda3\envs\myenv;C:\Users\username\anaconda3\envs\myenv\Library\mingw-w64\bin;C:\Users\username\anaconda3\envs\myenv\Library\usr\bin;C:\Users\username\anaconda3\envs\myenv\Library\bin;C:\Users\username\anaconda3\envs\myenv\Scripts;C:\Users\username\anaconda3\envs\myenv\bin;C:\Users\username\anaconda3\condabin;C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v11.2\bin;C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v11.2\libnvvp;C:\Program Files (Free)\Python37\Scripts;C:\Program Files (Free)\Python37;C:\windows\system32;C:\windows;C:\windows\System32\Wbem;C:\windows\System32\WindowsPowerShell\v1.0;C:\windows\System32\OpenSSH;C:\Program Files (x86)\NVIDIA Corporation\PhysX\Common;...（文字数制限のため以下省略）...'
    with kwargs:
{'stdin': -1, 'stdout': None, 'stderr': None, 'cwd': None, 'close_fds': False}

[NbConvertApp] ERROR | [WinError 2] 指定されたファイルが見つかりません。
Traceback (most recent call last):
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_client\manager.py", line 351, in _async_start_kernel
    await ensure_async(self._launch_kernel(kernel_cmd, **kw))
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_client\utils.py", line 34, in ensure_async
    return await obj
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_client\manager.py", line 269, in _async_launch_kernel
    connection_info = await self.provisioner.launch_kernel(kernel_cmd, **kw)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_client\provisioning\local_provisioner.py", line 179, in launch_kernel
    self.process = launch_kernel(cmd, **scrubbed_kwargs)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_client\launcher.py", line 169, in launch_kernel
    raise ex
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_client\launcher.py", line 157, in launch_kernel
    proc = Popen(cmd, **kwargs)
  File "C:\Users\username\anaconda3\envs\myenv\lib\subprocess.py", line 951, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "C:\Users\username\anaconda3\envs\myenv\lib\subprocess.py", line 1420, in _execute_child
    hp, ht, pid, tid = _winapi.CreateProcess(executable, args,
FileNotFoundError: [WinError 2] 指定されたファイルが見つかりません。
Traceback (most recent call last):
  File "C:\Users\username\anaconda3\envs\myenv\lib\runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "C:\Users\username\anaconda3\envs\myenv\lib\runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "C:\Users\username\anaconda3\envs\myenv\Scripts\jupyter-nbconvert.EXE\__main__.py", line 7, in <module>
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_core\application.py", line 264, in launch_instance
    return super(JupyterApp, cls).launch_instance(argv=argv, **kwargs)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\traitlets\config\application.py", line 846, in launch_instance
    app.start()
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbconvert\nbconvertapp.py", line 361, in start
    self.convert_notebooks()
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbconvert\nbconvertapp.py", line 533, in convert_notebooks
    self.convert_single_notebook(notebook_filename)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbconvert\nbconvertapp.py", line 498, in convert_single_notebook
    output, resources = self.export_single_notebook(notebook_filename, resources, input_buffer=input_buffer)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbconvert\nbconvertapp.py", line 427, in export_single_notebook
    output, resources = self.exporter.from_filename(notebook_filename, resources=resources)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbconvert\exporters\exporter.py", line 186, in from_filename
    return self.from_file(f, resources=resources, **kw)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbconvert\exporters\exporter.py", line 204, in from_file
    return self.from_notebook_node(nbformat.read(file_stream, as_version=4), resources=resources, **kw)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbconvert\exporters\notebook.py", line 32, in from_notebook_node
    nb_copy, resources = super().from_notebook_node(nb, resources, **kw)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbconvert\exporters\exporter.py", line 143, in from_notebook_node
    nb_copy, resources = self._preprocess(nb_copy, resources)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbconvert\exporters\exporter.py", line 323, in _preprocess
    nbc, resc = preprocessor(nbc, resc)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbconvert\preprocessors\base.py", line 47, in __call__
    return self.preprocess(nb, resources)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbconvert\preprocessors\execute.py", line 80, in preprocess
    with self.setup_kernel():
  File "C:\Users\username\anaconda3\envs\myenv\lib\contextlib.py", line 119, in __enter__
    return next(self.gen)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbclient\client.py", line 460, in setup_kernel
    self.start_new_kernel(**kwargs)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbclient\util.py", line 84, in wrapped
    return just_run(coro(*args, **kwargs))
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbclient\util.py", line 62, in just_run
    return loop.run_until_complete(coro)
  File "C:\Users\username\anaconda3\envs\myenv\lib\asyncio\base_events.py", line 642, in run_until_complete
    return future.result()
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbclient\client.py", line 416, in async_start_new_kernel
    await ensure_async(self.km.start_kernel(extra_arguments=self.extra_arguments, **kwargs))
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\nbclient\util.py", line 96, in ensure_async
    result = await obj
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_client\manager.py", line 362, in _async_start_kernel
    raise e
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_client\manager.py", line 351, in _async_start_kernel
    await ensure_async(self._launch_kernel(kernel_cmd, **kw))
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_client\utils.py", line 34, in ensure_async
    return await obj
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_client\manager.py", line 269, in _async_launch_kernel
    connection_info = await self.provisioner.launch_kernel(kernel_cmd, **kw)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_client\provisioning\local_provisioner.py", line 179, in launch_kernel
    self.process = launch_kernel(cmd, **scrubbed_kwargs)
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_client\launcher.py", line 169, in launch_kernel
    raise ex
  File "C:\Users\username\anaconda3\envs\myenv\lib\site-packages\jupyter_client\launcher.py", line 157, in launch_kernel
    proc = Popen(cmd, **kwargs)
  File "C:\Users\username\anaconda3\envs\myenv\lib\subprocess.py", line 951, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "C:\Users\username\anaconda3\envs\myenv\lib\subprocess.py", line 1420, in _execute_child
    hp, ht, pid, tid = _winapi.CreateProcess(executable, args,
FileNotFoundError: [WinError 2] 指定されたファイルが見つかりません。

ここでusernameは自分のユーザ名を置換したものです。
自分のユーザ名は全てASCIIで表すことができるラテン文字で構成されています。

またmyenvもAnacondaの環境名を置換していますが、
全てASCIIで表すことができるラテン文字で構成されています。

「指定されたファイルが見つかりません。」と出ていますが、
実行するファイルは明らかに存在します。

試したこと

• Visual Studio Codeでは当該ipynbファイルは実行できることを確認しました
• ターミナルの再起動
• パソコンの再起動

補足情報（FW/ツールのバージョンなど）

• OS: Windows 10 Pro

バージョン情報

> conda --version
conda 4.10.3
> pip --version
pip 21.3.1 from C:\Users\ichikawa\anaconda3\envs\myenv\lib\site-packages\pip (python 3.9)
> python --version
Python 3.9.7
> jupyter --version
Selected Jupyter core packages...
IPython          : 7.30.0
ipykernel        : 6.5.0
ipywidgets       : not installed
jupyter_client   : 7.1.0
jupyter_core     : 4.9.1
jupyter_server   : not installed
jupyterlab       : not installed
nbclient         : 0.5.9
nbconvert        : 6.3.0
nbformat         : 5.1.3
notebook         : not installed
qtconsole        : not installed
traitlets        : 5.1.1