I figured out the issue. Below are some high level instruction for future reference in case anyone else is interested:
Heroku doesn’t work too well with SQLite (at least the way I had the project structured it seemed). So I created a PostgreSQL Database inside the Heroku application via the follow command:
$ heroku addons:add heroku-postgresql:hobby-dev
With the new PostgreSQL database you’ll need a few dependent library so that it works with the SQLite database that is in the web application. More specifically you’ll need psycopg2, but before you get psycopg2 you’ll need a few other things as well.
sudo apt install gcc
sudo apt install libpq-dev
sudo apt install psycopg2
I would recommend you take a look at the documentation for full details on installing psycopg2 as it was a bit more involved for my system.
See details at https://www.psycopg.org/docs/install.html
Now you just need to update the requirement text file with the new packages, just run.
Update requirements:
(venv) $ pip freeze > requirements.txt
Finally set the flask app path to the run Heroku flask_app command.
$ heroku config:set FLASK_APP=flaskr