Your boiler is currently set to summer mode, which means it is providing hot water but has intentionally turned off the central heating functions.

DIY fix possible

Locate the heating temperature control knob on the boiler front panel.Turn the knob clockwise away from the 'Sun' icon or leftmost position to a higher setting.Check if your external room thermostat or programmer is set to 'On' or 'Auto' and calling for heat.