Smart thermostat shows F.10 and cannot connect to the internet; remote control via Vaillant app not available.

Safety: Network troubleshooting only; no electrical work required.

• 1. Check router and internet: Confirm other devices can access the internet on the same Wi‑Fi network. Restart the router if needed.
• 2. Verify Wi‑Fi credentials: On the thermostat or in the Vaillant app, re‑enter the correct Wi‑Fi SSID and password. Ensure you are using a 2.4 GHz network if the device does not support 5 GHz.
• 3. Improve signal strength: Move the router closer to the thermostat/gateway or add a Wi‑Fi extender. Avoid thick walls or metal cabinets between them.
• 4. Check router settings: Ensure MAC filtering, parental controls, or firewall rules are not blocking the Vaillant device. Allow outbound connections and UPnP if recommended by Vaillant.
• 5. Reboot thermostat/gateway: Power cycle the Vaillant internet module or thermostat. Wait several minutes for reconnection.
• 6. Replace Wi‑Fi module if needed: If all network settings are correct and other devices work, but F.10 persists, the Wi‑Fi module in the thermostat or gateway may be faulty and require replacement.