By default, most operating systems will cache IP addresses and other Domain Name System (DNS) records in order to fulfill future requests more quickly.
Then, once you change the nameservers for your domain > your computer will try to load old DNS of your domain and by this will fail to load the website.
It's most likely local DNS cache, in this case - to clear that, the client can do the following.
Important! For both Mac and Windows: Close all browser windows.
On a Mac:
1. Open the Terminal.
2. Run the following command
sudo killall -HUP mDNSResponder && echo macOS DNS Cache Reset
After clearing the DNS cache you can then try accessing the domain or website again that was having issues.
On Windows:
1. Launch the start menu by pressing the Windows key and search for “CMD.” This should return the command prompt.
2. Run the following command
ipconfig /flushdns
You will then see a confirmation that it has successfully flushed the DNS resolver cache.
Flushing DNS will clear any IP addresses or other DNS records from your cache. This can help resolve security, internet connectivity, and other issues.
After clearing the DNS cache, they can then try accessing the domain or website they were having issues with.
