Setup subdomain in digital ocean and namecheap

I had bought a domain in namecheap, and want to setting up my subdomain in digital ocean. Currently I only had one droplet and running ubuntu linux 14.04. My site was running in grunt at null:3000 which is localhost:3000. In apache2 conf, I had used proxypass redirect to my site. Right now, things are getting weird, my domain.com works yesterday, but today doesn’t work anymore.

NameCheap

• NS Record to digital ocean ns1, ns2 and ns3
• A Record mydomain.com ip_address_droplet
• A Record subdomain.mydomain.com ip_address_droplet

Digital Ocean

• A Record mydomain.com ip_address_droplet
• A Record subdomain.mydomain.com ip_address_droplet
• NS Record to digital ocean ns1, ns2 and ns3 Apache2 Configuration

000-default.conf

<VirtualHost *:80>

        ServerAdmin webmaster@localhost
        ServerName www.mydomain.com
        DocumentRoot /var/www/mydomain

        ErrorLog ${APACHE_LOG_DIR}/error.log
        CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

subdomain.mydomain.com.conf

<VirtualHost *:80>
        ServerAdmin webmaster@localhost
        DocumentRoot /var/www/subdomain
        ServerName subdomain.mydomain.com

        <Directory /var/www/subdomain>
        Options Indexes FollowSymLinks MultiViews
        AllowOverride all
        Order allow,deny
        allow from all
                Require all granted
    </Directory>


        <Location />
                ProxyPass http://localhost:3000/
                ProxyPassReverse http://localhost:3000/
        </Location>

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined

</VirtualHost>

/etc/apache2/sites-available/000-default.conf used for mydomain.com /etc/apache2/sites-available/subdomain.mydomain.com.conf for subdomain. I had used a2ensite command to activate my subdomain, but the site doesn’t work, it show the site can’t be reached. Currently, both sites doesn’t work.