Thermostat shows E6 and cannot connect to Wi‑Fi or Alexa app

Note: This is a network issue; HVAC power can remain on.

• Check Wi‑Fi band: Ensure your router has 2.4 GHz enabled. The Amazon Smart Thermostat typically connects only to 2.4 GHz networks.
• Move or adjust router: If the thermostat is far from the router, move the router closer or add a Wi‑Fi extender. Walls and metal ducts can weaken signal.
• Re-enter credentials: In the Alexa app, forget the thermostat and re-add it, carefully entering the Wi‑Fi password.
• Router reboot: Power cycle your router and modem. Wait 2–3 minutes, then retry connection.
• Check firewall settings: Ensure your router is not blocking outbound connections for the thermostat (no strict MAC filtering or client isolation).

If E6 persists while other devices connect fine and signal is strong, the thermostat’s Wi‑Fi module may be defective and the thermostat should be replaced.