did you keg? bottle? if you bottled, did you move the beer to a different bucket and add sugar or just add sugar to the primary? how long did you let it primary or secondary? if you added sugar to a secondary then bottled from there, how much sugar did you add? if this is the case, how long have the bottles sit at what temp?
don't really want to have to ask so many questions, but they are all relevant. your question is like saying " i put gas in my car, and it won't start? why? "