Thermostat shows 'No Wi‑Fi' or a Wi‑Fi icon with an X, and cannot be controlled from the app.

Safety first: No need to open HVAC equipment; this is a low-voltage/network issue.

Steps to troubleshoot:

• 1. Enable Wi‑Fi: On the thermostat, go to Menu > Wi‑Fi and ensure Wi‑Fi is turned ON.
• 2. Check network band: Many Resideo smart thermostats require a 2.4 GHz network. Ensure your router is broadcasting 2.4 GHz and that the SSID is visible.
• 3. Move router or add extender: If the thermostat is far from the router, relocate the router or add a Wi‑Fi extender to improve signal strength.
• 4. Forget and re-add network: On the thermostat, forget the current network and re-enter the SSID and password carefully.
• 5. Check for firmware update: If the thermostat briefly connects, use the app or thermostat menu to check for and apply firmware updates.
• 6. Hard reboot: Remove the thermostat from the wall plate for 60 seconds, then reattach to reboot the Wi‑Fi module.

When to call a professional: If Wi‑Fi remains unavailable while other devices connect fine, the thermostat's Wi‑Fi module may be defective, and the thermostat should be replaced.