Nest thermostat shows N4 and cannot connect to the Nest service after a router or ISP change

Note: This is a network configuration issue.

• Disable client isolation: In router settings, turn off AP isolation or client isolation so devices on Wi‑Fi can communicate with each other and the internet.
• Security mode: Use WPA2‑Personal or WPA3‑Personal without enterprise authentication. Avoid mixed enterprise modes.
• Captive portal: If your ISP router uses a web login page, bridge it to your own router or request a standard configuration from the ISP.
• Firewall rules: Temporarily relax firewall settings to test. Ensure outbound HTTPS traffic is allowed.
• Re‑add Wi‑Fi: Forget the network on the Nest and re‑add it after router changes are applied.