Thermostat powers on but does not call for heat even when room temperature is below setpoint

Safety first: Turn off power to the thermostat and boiler/HVAC before touching wiring.

Steps to troubleshoot:

• Verify the thermostat is in HEAT or AUTO mode and the setpoint is above the current room temperature.
• Listen for a relay click inside the thermostat when raising the setpoint; absence of a click may indicate a relay or control fault.
• Check wiring from the thermostat heating output terminals (e.g., NO/COM) to the boiler or zone valve; ensure connections are tight and match the Tuya wiring diagram.
• With power off, test continuity across the thermostat heating relay contacts while commanding heat (using a bench supply or test mode if available). If the relay never closes, the relay is faulty.
• Replace the thermostat or main PCB if the relay is defective.
• If the relay closes but the boiler does not start, troubleshoot the boiler control circuit separately.