404 Nginx Ubuntu Error When Not Using WWW

A 404 is NGINX's default way of saying that a file or directory doesn't exist. If you're seeing a 404, it means that NGINX can't find the info it needs to serve when queried. The good news is that since you're seeing a 404, your A/AAAA records are pointing to the right IP; it's just that when it gets there, it can't find what it's looking for.

You'll want to double check your sites-available configuration (the file should be located in /etc/nginx/sites-available/example.com) and make sure your symlinks between sites-available and sites-enabled (/etc/nginx/sites-enabled/) are set up properly. Just in case, you'll also want to double check your /etc/hosts file configuration to make sure your IP is pointing to the correct FQDN.

We have instructions for setting up your /etc/hosts/ file in our Getting Started guide here, but here's a quick default config:

127.0.0.1 localhost.localdomain localhost
203.0.113.10 example-hostname.example.com example-hostname
2600:3c01::a123:b456:c789:d012 example-hostname.example.com example-hostname

Likewise, here's a good example of a healthy sites-available config from our NGINX guide. Keep in mind, this is a basic setup with NGINX only being configured for HTTP connections on port 80:

server {
    listen  80;
    listen [::]:80;
    server_name example.com;

    root /var/www/example.com;
    index index.html;

    location / {
        try_files $uri $uri/ =404;
    }
}

For what it's worth, I set up a basic site on a Linode solely running NGINX with A/AAAA records for my site with and without "www", and it worked like a charm using the Getting Started and NGINX guides I linked above.

I also tracked down a nice post from NGINX's official site with tons of configuration troubleshooting tips: NGINX: Pitfalls and Common Mistakes

It turned out to be an issue with certbot and the changes it made to the /sites-enabled/config file.