How can I fix my vokera combi boiler ( 14 years old)?

I have very little water flowing through the hot water taps thus the boiler will not ignite. (It ignites if central heating is requested) I have tried to increase the presure but nothing is happening ( its just at 1 bar). I reckon I will have to call out an engineer unless anyone can help in layman terms!!!! The boiler runs on LPG.and was fully serviced one year ago.