step#1 if you are using an internet connection via a router then Try to restart the router
step#2 And then next Restart your PC
step#3 If you are using the internet via a smartphone then try a flight to mode wait sometimes and then turn off flight mode
step#4 You can also install DNS Angel. This application will help you to easily change DNS IPs so that even if your system is unaware of nameservers, change it. DNS Angel automatically fetches the current nameservers from DNS and allows you to access your server.
For Download DNS Angel You can download it from here
We hope this information helps you