Heating not coming on - Worcester Greenstar 37cdi?

I have a Worcester Greenstar 37cdi and currently the heating is not being triggered by the Digistat RF3. We haven't had the heating on for a few months but have not changed any settings. The boiler is working fine it seems for the underfloor heating (also via a seperate Digistat RF3) as is the hot water. I have seen other posts regarding a non functioning Digistat and have checked batteries, receiver, etc - the remote is communicating with the receiver and the receivers green light is going on, so the boiler should start but it doesn't. Bar pressure is above one, no other issues as far as I can tell. Can anyone advise? thanks.