Python can't find local files/modules

I’m setting up a Flask application on Digitalocean and have Python 3.7 installed and the latest version of Flask. When running the app inside a virtualenv and trying to run the application using python3.7 application.py I get the following error message:

Traceback (most recent call last):
    File "application.py", line 11, in <module>
        from config import *
ModuleNotFoundError: No module named 'config'

What puzzles me is that config.py is located in the same folder as application.py, and not in a subfolder. I have duplicated the setup on my local machine, also running Python 3.7 and inside a virtualenv, and the importing (and the app) works flawlessly.

I’ve tried importing “config.py” instead of just “config” but didn’t make a difference. I also tried specifying exactly what it should import (instead of using ‘*’) but that didn’t make a difference either.

Your thoughts on why it can’t find config?