macOS port mapping connection refused

I’ve followed the steps provided in the lesson https://kodekloud.com/courses/296044/lectures/4554709 and when I run docker run -p 80:5000 some-name the Flask app runs but I get a “The connection was reset” in Firefox. I’m on macOS 10.15.4.

https://hub.docker.com/repository/docker/ricardoaugusto/simple-flask-app

Why is that?