Step 1: Check your Nameservers.
intoDNS is very helpful to get further insight to your DNS issues. Visit http://intodns.com/ and enter your domain name: you will want to check both prefixes: domain.com + www.domain.com
Additionally, DNSViz is excellent for diagnosing DNSSEC associated issues.
DNSSEC errors can happen when switching DNS providers, or after premium DNS has been discontinued. If this happens, delete your DNSSEC settings.
(stop at any point when you’ve discovered the underlying issue.)
Step 2: Verify you can connect to Google’s Public DNS servers.
Open a terminal window and run the following commands:
If you cannot connect, or if you experience significant timeouts signal that you have a network problem preventing you from accessing the servers.
Step 3: Verify your Hostname is reachable.
Again, in a terminal window, enter the following commands, replacing “example” with the URL you are having issues with. Check for errors that could signal what the problem with your DNS resolution is.
*IPv6 might not work for all users, if it doesn’t work, skip to step 4. Replace example.com with your actual domain name.
Step 4: Verify your DNS without performing a DNSSEC validation.
If you cannot connect, it would signal that your issue might not be DNSSEC related. If you can connect, it means you have a DNSSEC misconfiguration.
Step 5: Verify other Servers can connect.
Enter the following command prompts.
If nothing happens, it could mean you have tempory DNS resolution issues. Wait and re-test. At this step, if you are still unsuccessful and not sure what to do, its best to get assistance from a DNS professional.