no live upstreams while connecting to upstream

Hi Guys,

no live upstreams while connecting to upstream - Really fed up from this error. any help would be really appreciated.

below is the file content of /etc/nginx/sites-available/example.com

server {
        server_name example.com www.example.com;
        root /var/www/shopify/First/html;
        index index.html;
        location / {
                proxy_pass http://localhost:3000;
                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 ($host = www.example.com) {
        return 301 https://$host$request_uri;
    } # managed by Certbot
    if ($host = example.com) {
        return 301 https://$host$request_uri;
    } # managed by Certbot
        listen 80;
        listen [::]:80;
        server_name example.com www.example.com;
        return 404; # managed by Certbot
        }

It is working for IP address(but only index.html). Path for node js app is not opening for IP address.

node js app is working for localhost:3000

kindly help.

thanks in advance.