Follow these steps to troubleshoot the “Error: Network connection failed” message:

1. Check Physical Connections: Ensure that all cables are securely connected to the modem and router.
2. Restart Devices: Power off your modem and router. Wait for 30 seconds, then turn them back on.
3. Check Device Connections: Verify that your device is connected to the correct Wi-Fi network.
4. Run Network Troubleshooter: On Windows, go to Settings > Network & Internet > Status. Click on “Network troubleshooter” and follow the prompts.
5. Update Network Drivers: On your computer, check for driver updates for your network adapter.
6. Flush DNS Cache: Open Command Prompt and type `ipconfig /flushdns`, then hit enter.
7. Check for Service Outages: Visit your Internet Service Provider’s (ISP) website or contact them to see if there are known service issues in your area.
8. Reset Network Settings: If you’re using a mobile device, go to Settings > General > Reset > Reset Network Settings.
9. Change DNS Settings: Consider using public DNS servers like Google DNS (8.8.8.8 and 8.8.4.4) for potentially improved connectivity.
10. Factory Reset Router: If all else fails, perform a factory reset on your router (note that this will erase all your settings).

These steps will guide you in diagnosing and resolving the network connection failure issue effectively.