what is wrong with my potterton boiler?

I have a potterton boiler and as it has been hot for the last week or so, i have turned the heating off. although today i went to the boiler and the low pressure light is on and the flame one is off. i have repressurised the boiler to about 2.5 and tried resetting the boiler simply by pressing the button, but with no luck....does anyone know wat is wrong with it? or have i tried to reset it wrong?
thank you!