Then in the Preferred DNS Server field type in 18.104.22.168 and in the Alternate DNS Server field type in 22.214.171.124 then check Validate Settings Upon Exit box and click OK. This will change the DNS servers on only the computer.
If you are using internet on a mobile using a router then you can check out this post on how to change DNS servers on routers.
Windows and other operating systems usually store the DNS data in the cache This cache also store data of the visited websites and clearing the cache may solve the problem.
To do that, click the Start button and type in cmd in the search box and press Enter from keyboard.
In our case we will use Google’s DNS server address. Windows 10 Users can simply type in into the Windows search box and press Enter.
You can also Press on the Windows key from your keyboard and start typing which will take you to the search box.A new window will pop up, select Internet Protocol Version 4 (TCP/IPv4) and then click Properties again.In that window select the radio button that says Use the following DNS server Addresses.At this point we will change the physical address of the computer.Go to Windows Start menu and type in cmd in the search box and hit Enter.You can also try to connect a second device like a tablet or someone else’s laptop either wirelessly or wired to your network.Now try to browse that particular website and check if you still get the DNS Server Not Responding or DNS Server Unavailable error.Disable the connections that you are not using by right clicking on them and then clicking Disable.In the picture above I’ve right clicked on the network that I’m using because the other ones are already disabled.If not then also type in the following command and press Enter after each of them.Once done, restart your computer and check if the problem still exists.