Problems with deploying on AWS EC2

I tried to deploy for the first time a MERN app on the AWS EC2.

I completed this article's steps, except for installing the mongodb, because I used Ubuntu 20.04 instead of 16.04, I used the docs and it had worked.

In the end I opened the app.js from /server/dist with pm2 and I had got the status of working, but when I wanted to access the website, it said that the connection was refused.

This is my github repository.

If you have time and experience with AWS EC2, please check it! I didn't find anything, why it wouldn't work.