I have a Conda environment with Python 3.9.19 and scripts that import a library (FiftyOne).
Everything works fine.

I tried to upgrade Python version to 3.11.9, but when I execute my script, I get the following error:

ModuleNotFoundError: No module named ‘fiftyone’
I wonder why it doesn’t work anymore. Is it an error on Python side or FiftyOne?

Each Python installs modules separately. If you install new version, you have to reinstall all required modules again for new Python runtime.