pip install worked. The module is still missing.

This happens because pip and python are two separate commands — they can point to different Python installations. pip installs to one; your script runs on another.

Most common fix — try this first
python -m pip install [package]

python -m pip guarantees the install goes into the same Python that runs your script. If this fixes it, you're done. If not, the diagnostic below finds the exact cause.

2-minute diagnostic

Run two commands, paste the output

This identifies which of the 6 common root causes matches your setup.

Run these in your terminal:

pip --version
python3 --version

Paste the full output of each command exactly as shown in your terminal.