Restart Modem and Router:

Disconnect power for 30 seconds. Start modem first, wait for connection. Then restart router. Fixes 50% of issues.

Run Network Troubleshooter:

Settings > Network & Internet > Network troubleshooter. Windows diagnoses and attempts automatic repair.

Reset Network Settings:

Settings > Network & Internet > Advanced > Network reset. Restores all network settings to default. You'll need to reconnect to networks.

Update Network Driver:

Device Manager > Network adapters. Update driver for your adapter. Or uninstall and restart for automatic reinstallation.

Reset TCP/IP Stack:

Command Prompt as Administrator. Run "netsh int ip reset" then "netsh winsock reset". Restart computer after.

Check Cables:

For wired connections: try different Ethernet cable. Ensure proper port connection on router. LEDs should light up.

Conclusion:

Modem/router restart is always first step. Network reset is powerful but requires reconfiguration afterwards.