[change domain] digital ocean droplet issue

Hello there,

Today, I'm facing very difficult situation regarding 'changing domain name on digitalocean droplet'.

Currently My domain returns ‘welcome to nginx server’.

wordpress : Installed wordpress 3.9.1 multisite + w3 + nginx helper.

1. I’ve done DNS setting and domain is correctly pointing my droplet’s IP address. (digitalocean)
2. I have existing DB on my droplet and trying to connect my new domain with existing droplet
3. I did everything correctly with below script.

cp -v /etc/nginx/sites-available/old-domain.com /etc/nginx/sites-available/new-domain.com
vim /etc/nginx/sites-available/new-domain.com

cp -av /var/www/example.com/htdocs /var/www/example.com/wp-config.php /var/www/mydomain.com
ee site enable mydomain.com

4. When I typed ‘vim /etc/nginx/sites-available/new-domain.com’there are some lines that pointing my old-domain.com then I’ve changed those old-domain.com to my new-domain.com
5. Followed every steps + add some codes in wp-config.php

define(‘WP_HOME’,’http://example.com’);
define(‘WP_SITEURL’,’http://example.com’);

6. And add some codes on functions.php in theme folder

update_option(‘siteurl’,’http://example.com’);
update_option(‘home’,’http://example.com’);

7. Result?

* I cannot get connected to my new domain.
* When I trying to get connect to new-domain.com/wp-admin. It said ‘ there are redirection error’
And URL looks like this.

new-domain.com/wp-signup.php?new=new-domain.com

COULD YOU PLEASE HELP? My customers are complaining like hell.

Help~~~~~