Heating boiler through the programmer is on hot water ok no heating to rad?

Boiler operates in the hotwater mode, put the switch over to the heating,no heating,room stat on max, 3 port valve with lever loose and energised, only way at this moment to get heat is put the temp up on cylinder stat and leave heating switch in heating mode and heating circulates while hotwater reaches temp and goes off until hotwater used....is there any help out there.