Nginx - 502 Bad Gateway - No Upstreams

Hi Guys,

I am getting the following error when accessing domain linked droplet IP.

Droplet Ip address is opening but the domain linked to it is giving the below error.

2023/08/06 10:04:09 [error] 30587#30587: *15 no live upstreams while connecting to upstream, client: IP, server: example.com, request: "GET / HTTP/1.1", upstream: "http://localhost/", host: "example.com"

2023/08/06 10:07:06 [error] 30587#30587: *16 connect() failed (111: Unknown error) while connecting to upstream, client: IP, server: example.com, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:8080/", host: "example.com"

Please note that it’s a simple HTML page. I want to use with shopify app built in node js, but as of now checking with normal html page

Below is the code of sites-enabled/example.com:

upstream example.com {
        server example.com:443;
        server www.example.com:443;
}
server {
        server_name example.com;
        location / {
                proxy_pass http://localhost:8080;
                proxy_http_version 1.1;
                proxy_set_header Upgrade $http_upgrade;
                proxy_set_header Connection 'upgrade';
                proxy_set_header Host $host;
                proxy_cache_bypass $http_upgrade;
        }

    listen [::]:443 ssl ipv6only=on; # managed by Certbot
    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

}

server {
    if ($host = example.com) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


        listen 80;
        listen [::]:80;
        server_name example.com;
    return 404; # managed by Certbot
}

Below is the code of sites-enabled/default

server {
        listen 80 default_server;
        listen [::]:80 default_server;

        root /var/www/html;

        # Add index.php to the list if you are using PHP
        index index.html index.htm index.nginx-debian.html;

        server_name _;

        location / {
                # First attempt to serve request as file, then
                # as directory, then fall back to displaying a 404.
                try_files $uri $uri/ =404;
                # proxy_pass http://localhost:8080;
                # proxy_http_version 1.1;
                # proxy_set_header Upgrade $http_upgrade;
                # proxy_set_header Connection 'upgrade';
                # proxy_set_header Host $host;
                # proxy_cache_bypass $http_upgrade;
        }
}

Any help would be really appreciated.

Thanks in advance :)