The "One or more of your nameservers did not respond" error

Symptoms

When setting up new nameservers, you may see errors occur during initial testing, such as:

One or more of your nameservers did not respond.

Description 

This error can occur for several reasons. However, the most common cause is usually related to port 53 being blocked or filtered for incoming DNS requests.

You can manually verify whether the ports are open from the outside by testing them from a remote server with the telnet command:

telnet SERVERIP 53

Please note, you will want to replace "SERVERIP" with the server's IP.

You can also query the server directly to see if it responds with records:

dig @SERVERIP A +trace yourdomain.tld

Please note, you will want to replace "SERVERIP" with the server's IP and "yourdomain.tld" with a domain.

Depending on your hosting provider, the steps necessary for opening the ports may vary. Our cPanel documentation here covers our requirements on how to configure your firewall for all cPanel-related services:

How to Configure Your Firewall for cPanel & WHM Services

Workaround

As a resolution to this issue, port 53 needs to be open in the server and network firewalls for both TCP and UDP traffic.