Ferroli Falcon II Ignition Wont Fire Up?

Hello. I have a Ferroli FER Falcon II Combi Boiler. The fan runs but the ignition does not fire up. However, I took the room seal front panel off and it works. I put the front panel back on and the ignition now fires but after a while it cuts out and fires back up again straight away. If I leave the front panel in place but not tightened up it stays on for much longer. I understand it could be the Air Pressure Switch or the Safety Overheat Stat. Same problem for heating and hot water. Can anybody confirm that?? Thanks. Graham.