Flexicom boiler does not cut in for radiators?

Flexicom 30cx boiler. Cuts in and gives hot water when the taps are used. When I turn on the heating via a remote system the small light on the receiver comes on but the boiler does not respond. Not even a click. If I turn it off and on and hit it a few times, sometimes it will work. Most of the time nothing happens. Is there a relay and is it easy to replace ??