I have a Vokera Linea 28 combi boiler I had to move it recently, and to reduce the pressure to cut the pipes I opened the drain valve on the lowest radiator(radiators were not drained completely). Our gas fitter came back & reconnected the gas, but to repressure using the filling loop the pressure wont rise & no water can be heard running in. Our gas fitter has got the flu and so wont be back for some time. This is a problem as we live in a very remote area and he is the nearest guy Anybody got any idea what could be wrong?