you will need to repressurise your pressure vessel big red thing at back , to do this blow pressure off turning little red knob. then pump up the vessel by using foot pump to 1 bar, after this refill boiler yo 1bar
either your diagphragm has split in your pressure vessel or it might need repressurising . to do this you must release the pressure first then pump the presure vessel up with a foot pump, if you look you can see the nipple, pump it up to 1 bar once you have done this refill the boiler to 1 bar ...