Thermostat displays E40 and reports a configuration mismatch; system does not heat or cool correctly after setup.

Safety first: Turn off power to the HVAC system at the breaker before changing wiring.

• Review equipment type: Confirm whether your system is a heat pump or a conventional furnace + AC. Check the model numbers on your indoor and outdoor units if unsure.
• Verify wire mapping: Remove the Wyze display and note which colored wires are connected to which terminals. Compare this to the labels on your old thermostat (if available) and to the furnace/air handler control board terminals.
• Re-run Wyze setup: In the Wyze app, delete the thermostat and re-add it, carefully answering the wiring and system-type questions to match your actual equipment.
• Set O/B correctly for heat pumps: If you have a heat pump, consult the outdoor unit’s manual to determine whether the reversing valve is energized in heat or cool, and set this option correctly in the Wyze app.
• Test all modes: After configuration, test heating, cooling, and fan-only modes to ensure correct operation and that E40 clears.