Thermostat displays E5 and Wi‑Fi or app connectivity is unavailable

Safety: No high-voltage work is required, but avoid opening the thermostat housing beyond the user-removable front.

• Power cycle: Turn off the HVAC breaker for 60 seconds, then restore power to reboot the thermostat and Wi‑Fi module.
• Check router: Ensure the router is powered, broadcasting 2.4 GHz (most Lux smart thermostats do not support 5 GHz only), and that SSID is visible.
• Forget and rejoin network: On the thermostat menu, navigate to Wi‑Fi settings, select your network, choose "Forget" or "Disconnect", then re-add the network and re-enter the password.
• Update firmware: Using the Lux mobile app, check for firmware updates and apply any available update while the thermostat is temporarily connected.
• Factory reset: If E5 persists, perform a factory reset from the settings menu (note: this will erase schedules and custom settings).
• Replace thermostat: If the Wi‑Fi module still fails to initialize after reset and router checks, the internal Wi‑Fi board is likely defective and the thermostat should be replaced.