Thermostat display is completely blank and does not respond to button presses or app commands.

Safety first: For mains‑powered units, isolate power at the breaker before removing the thermostat from the wall.

Steps:

• Check batteries: For radiator thermostats, replace both AA batteries with new alkaline cells, ensuring correct polarity.
• Verify mains power: For wall thermostats, check the circuit breaker and confirm voltage at the thermostat terminals with a multimeter.
• Inspect connections: Ensure all wires are firmly secured in the backplate terminals and that the thermostat is correctly docked onto the backplate.
• Replace unit: If power is present but the display remains dead, the internal electronics are likely faulty and the thermostat should be replaced.