Boiler does not respond to the room thermostat or programmer; it stays off.

Safety first: Isolate power before handling wired controls.

User checks:

• Thermostat batteries: Replace batteries in wireless thermostats and re-pair if necessary.
• Programmer settings: Ensure heating and hot water are set to ON or timed, not OFF.
• Manual boiler control: Increase the boiler's own thermostat and check if it fires when there is a demand.

If the boiler still does not respond, an engineer should test control circuits and replace faulty controls or repair wiring.