why won't our new controller work?

we have just replaced our rf thermostat and reciever on our oil boiler from a drayton digistat + rf to a siemens RDH10rf/set-gb and cannot get the central heating to work properly we have hot water but the red light is staying on all the time saying there is no signal being recieved. the timer is still the old danfoss that was originally put in when we had the boiler replaced in 2007, the boiler has been serviced and we were told that it was an elecrtical fault nothing to do with the boiler. please can you give us any advice?