Nginx – How to point CNAME to Digital Ocean droplet

Having an issue trying to point a CNAME to my Digital Ocean droplet

I created a CNAME on DNSimple and pointed it to the IP address of my Digital Ocean droplet: ironman4x4.adamgeorge.com

I've tested that it exists:

→  ~  host -t cname ironman4x4.adamgeorge.com
ironman4x4.adamgeorge.com is an alias for 128.199.176.45.

My Digital Ocean droplet was created using this guide:

https://www.digitalocean.com/community/tutorials/how-to-use-the-1-click-ruby-on-rails-on-ubuntu-14-04-image

The 1-click install creates a default site here which I tried customising the root and server_name options:

server {
        listen   80;
        root /home/rails/current/public;
        server_name _ ironman4x4.*;
        index index.htm index.html;

        client_max_body_size 5M;

        location / {
                try_files $uri/index.html $uri.html $uri @app;
        }

    location ~* ^.+\.(jpg|jpeg|gif|png|ico|zip|tgz|gz|rar|bz2|doc|xls|exe|pdf|ppt|txt|tar|mid|midi|wav|bmp|rtf|mp3|flv|mpeg|avi)$ {
                        try_files $uri @app;
                }

         location @app {
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header Host $http_host;
                proxy_redirect off;
                proxy_pass http://app_server;
    }

}

Not sure why it's not working.

I can't SSH onto the server via ssh root@ironman4x4.adamgeorge.com, nor does Nginx respond via http://ironman4x4.adamgeorge.com

Not sure why?

Is there anything else I need to configure for either the DNS or or the droplet to get this to work?