Finally managed to get CO2 for my tap system, but I've had another snag. Flat beer. I've got a keg of black lager and a keg of Irish red ale in there, both of which taste great, but are flat as the proverbial pancake. I've tried cranking up the psi on the regulator, checked for leaks, nothing. Can't figure out what I'm doing wrong. I've probably overlooked something vital... 'elp!