Follow these steps
1
Test another device on the same Wi-Fi to identify whether the problem is the router or one computer.
2
Restart the router: unplug it for 30 seconds, reconnect it and wait two minutes.
3
On Windows, forget the Wi-Fi network, reconnect and enter the password again.
4
Open Command Prompt as Administrator and run: ipconfig /flushdns, then netsh winsock reset.
5
Restart the computer after running the commands.
6
If only websites fail, set DNS to automatic first; then try a trusted DNS service only if you understand the change.