Failed build in RTD for extension sphinx-copybutton

[SinChan4896]

Describe the bug

Context
This is the duplicate question from this Github report

Error
Error in RTD
Could not import extension sphinx_copybutton (exception: No module named 'sphinx_copybutton')

Issue
I got the same issue as the reporter where the copy icon is works on local but failed when uploading in RTD. In the article above stated need to follow this RTD Build and this Config V2.
Then i created the .readthedocs.yaml and requirement.txt. So is it both .yaml and .txt are in wrong dir or missing context?

Reproduce the bug

1. pip install sphinx-copybutton
2. In the conf.py add this
   extensions = [
   ...
   'sphinx_copybutton'
   ... ]
3. added .readthedocs.yaml and requirement.txt
4. git add -A
5. git commit -m "Create xxx"
6. git push
7. The RTD tab Build is failed.

List your environment

Version: 1.67.1 (user setup)
Electron: 17.4.1
Chromium: 98.0.4758.141
Node.js: 16.13.0
V8: 9.8.177.13-electron.0
OS: Windows_NT x64 10.0.19044

Package (Version)

alabaster 0.7.12
appdirs 1.4.4
Babel 2.10.1
certifi 2021.10.8
charset-normalizer 2.0.12
colorama 0.4.4
docutils 0.17.1
esbonio 0.11.2
idna 3.3
imagesize 1.3.0
Jinja2 3.1.2
MarkupSafe 2.1.1
packaging 21.3
pip 22.1
pydantic 1.8.2
pygls 0.11.3
Pygments 2.12.0
pyparsing 3.0.8
pyspellchecker 0.6.3
pytz 2022.1
requests 2.27.1
setuptools 62.3.1
snowballstemmer 2.2.0
Sphinx 4.5.0
sphinx-bernard-theme 0.1.12
sphinx-copybutton 0.5.0
sphinx-rtd-theme 1.0.0
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
typeguard 2.13.3
typing_extensions 4.2.0
urllib3 1.26.9