Book built successfully but html not found

[Hejia1234]

Hi jb community!

I'm new to jb and I'm following this link https://jupyterbook.org/en/stable/start/build.html, to build a book.

My question is, although it shows "Finished generating HTML for book", when I copy the /index.html, I got "file not found" error.

Does anyone know how to solve this issue? Thank you!!