Your boiler is currently set to a state where the central heating function has been deactivated.

DIY fix possible

Check the control panel on the front of the boiler to ensure the heating mode is set to 'On' or 'Auto'Verify that your external room thermostat or wall-mounted timer is set to a temperature higher than the current room temperatureEnsure the central heating dial on the boiler control panel is turned up to a mid-to-high setting