digistat rf3 SCR wont talk to boiler?

i am installing a digistat rf3 to replace a previous digistat. the scr and remote digistat programmer/thermostat are communicating with each other but not with the boiler. the boiler comes on as soon as the fused power switch is turned on and so it works . the boiler just isnt controlled by the scr for coming on and going off. i have followed wiring in diagram so now stuck. it is a combi boiler but only does central heating now. i am sure it is just an incorrect or missing loop in the circuit in scr but i am now stuck. help please