

I prefer a really well told story over a pick your own adventure. Character flaws, growth, emotional connections and situational realities are all able to be masterfully written when in control. But if you can’t write well, just make an interesting playground and leave it up to the player and blame them for a boring game. :)
404 is a web server response suggesting that a web server is up. It’s what’s giving 404.
The web server can’t find your page or document or resource. So one of your web servers (on either the reverse proxy or the actual server) is pointing to the wrong spot on what to serve.
You haven’t tried launching a wrong server on the same port right? Or misconfigured your nginx translation?
Isolate the issue. Ignore nginx and start testing just the web server on the destination and see if the server is giving 404 and then if it is giving the right document then it’s nginx configuration. If it’s not giving you the document nginx can’t serve.
But either way start isolating the problem into the smallest area. And focus on the configurations and files that are related to it.