After you change the nameservers for your site, you will want to clear the DNS cache.
For Windows OS:
Search Windows for “cmd” (Command Prompt). In the Command Prompt window, type ipconfig /flushdns
Microsoft Windows [Version 10.0.15063] (c) 2017 Microsoft Corporation. All rights reserved. C:\Users\Max>ipconfig /flushdns Windows IP Configuration Successfully flushed the DNS Resolver Cache. C:\Users\Max>
Windows Command Prompt
If you are using a recent version of Windows – like Windows 10 – you can also use the Windows PowerShell. Use the same command ipconfig /flusdns :
Windows PowerShell Copyright (C) 2016 Microsoft Corporation. All rights reserved. PS C:\Users\Max> ipconfig /flushdns Windows IP Configuration Successfully flushed the DNS Resolver Cache. PS C:\Users\Max>
Some browsers keep a DNS cache which is independent from the one used by the OS. For example, in Google Chrome, navigate to chrome://net-internals/#dns and click the “Clear host cache” button.
Google Chrome Clear host cache
You can also clear the DNS cache for your domain at the Google Flush Cache