Thermostat displays E04 and cannot connect to Wi‑Fi network

Safety first: Network configuration changes are low risk, but avoid resetting your router unless you know the consequences for other devices.

• Check signal strength: On the thermostat Wi‑Fi setup screen, check the reported signal level. If very low, move your router closer or install a Wi‑Fi extender.
• Verify network details: Ensure you are connecting to a 2.4 GHz network (most smart thermostats do not support 5 GHz). Re-enter the Wi‑Fi password carefully, respecting case sensitivity.
• Router settings: Ensure MAC address filtering is disabled or that the thermostat's MAC address is allowed. Check that the router is not set to hide the SSID.
• Reboot devices: Restart your router and then power-cycle the thermostat. Retry the Wi‑Fi setup process.
• Factory reset Wi‑Fi: If E04 persists, perform a Wi‑Fi reset on the thermostat (refer to the manual) and set it up again from scratch.
• If still failing: The internal Wi‑Fi module may be defective. Replacement of the thermostat is usually required.