How can i fix my ferroli optimax combi boiler ( he31c )?

Hi, i have just moved into a property that has had a new boiler fitted, its a combi boiler ferroli optimax he31c i ve read through the instructions and i didnt help me at all. i cannot get the heating to come on ive pushed all the buttons and turned up the termostat but still nothing. in the booklet it says nothing at all about the timer which seems to be making everything not come on straight away. also the hot water doesnt always come on when it should ( it comes on hot then it wont work the next time i turn on the tap). could you give me any advice please