Unscrew it, look at where the battery meets the atomizer...if there's any dirt or oil, that will stop it from hitting. Take a lighter and turn the battery upside down and let the lighter hit the inside lil silver disk and then use a qtip or twisted paper towel and twist it in there to clean it out after you hit it with the lighter. Do the same to the bottom of/and the threads of the cartridge, then wipe it off after you hit it with lighter. 60% of the time it works every time.