Getting a 404 error while trying to visit site

[nathanmartin]

@dagger-v See:

[Support Guide] Can I run a web server, HTTP listener, and/or database at Netlify?

Last reviewed by Netlify Support on December 2022 How do I run a server/database at Netlify? We often get questions about how to run a specific backend server or database at Netlify. Examples of these types of questions include: How to I get my node HTTP listener to respond to requests? How do I start Mongo/MySQL/<insert-some-database-here> running on the server? How can I SSH into my website? We are here today to answer these questions - and the answer is: you can’t! What do you m…

TL;DR - You can’t host a Node.js server app with Netlify.

So you’ve deployed your source files to the CDN, e.g.
https://magenta-rabanadas-70a789.netlify.app/app.js

You can use Express with Serverless functions:

Express on Netlify