Proxying nginx to port 1337 with Strapi

Trying to make a proxy from domain: api.example.com to api.example.com:1337. The proxy is working sort of. If I use port 3000 (which is my main site) it all works, just not on 1337.

I have initialised the strapi-app with “yarn build”, and using pm2 to continuing run Node. Also making sure that port 1337 is allowed in the firewall.

Can anyone possible guess what the issue might be? I have tried almost everything I can think of :-)

This is my nginx configuration:

server {
    index index.html;
    server_name api.example.com;

    location / {
        proxy_pass http://api.example.com:1337;
        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;
    }
}

My ufw firewall settings:

To                         Action      From
--                         ------      ----
1337/tcp                   ALLOW       Anywhere
1337                       ALLOW       Anywhere
1337/tcp (v6)              ALLOW       Anywhere (v6)
1337 (v6)                  ALLOW       Anywhere (v6)

Strapi-app structure:

someuser@someuser-website:~/api$ ls
README.md  api  build  config  extensions  favicon.ico  node_modules  package.json  public  yarn.lock