In my case, I was working with a version of Miniconda and had installed a package with Python 3.6 for an OpenCV course. After trying a lot... and almost giving up, I realized that the Python version wasn't compatible with the autocomplete in VS Code. So, I created a new environment and installed the packages using pip... and everything worked. I installed Python version 3.8 — just leaving this here in case someone else is going through the same thing.