Pressing those buttons together is for tests, commisioning etc: not really wise to do so regularly.
When you are calling for CH, is the radiator symbol in the display?
If it isn't make sure the bottom thermostat dial is turned up sufficiently, if it still doesn't appear, the problem is highly likely to be external: Clock/room stat.
If it appears and you have no CH, most likely fault will be diverter valve.
Carefree, January 2011
