my appollo boiler, is lit, but not firering up,?

my boiler will not, fire up, i have done everything that should be done......i had a new bit of mechenisam fitted at the begining of the year, this is the peice that has the greybutton included on it, the button you press to fire it up.............all the power is ok, please help we are all freezing

lesley
October 2007