Just to point out I have been stumbling to this error when working with virtualenvs. If you're working with scripts, check how your shebang(#!/usr/bin/python3) invokes Python. Scripts run as ./script.py will invoke global Python Interpreter and will likely lead to a Module NoT Found Error because the module isn't installed system-wide. Instead run the script as python3 script.py to invoke the env's Python interpreter.

hope this helps