Room thermostat not calling for heat when required

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I have put my room thermostat in coldest room so it never reaches the set temperature I have set during the times I have it set to come on. The reason for this is because I have not put a radiator thermostat in the bathroom as I want this on all the time to tie in with the room thermostat. Something is not quite right as my room thermostat is not calling for heat when it should so my bathroom rad is not coming on. I have already checked for pairing to receiver and this is ok. Does anyone have any ideas why it is not working