vauxhall vivaro wont start cold or hot unless i use easy start then it runs and drives ok ,

it cut out on me once while going along,rac man said computer showed low pressure on fuel rail,started with easy start drove ok,had the same symptoms before fitted new pressure booster solonoid valve,started ok for about a week,back to no starting now,ps the p.b.s.valve had seized,appreciate any help i can get thanks,