I have a Taprite CO2 regulator (http://morebeer.com/products/dual-gauge-co2-regulator-taprite.html?site_id=5) and my regulator says there's CO2 in the tank, however when I try to turn the regulator knob to apply pressure to the keg it just clicks and no CO2 is being released into the keg, however if I remove the CO2 tank and open there's clearly gas in there. Is there just not enough gas to be added or is my regulator broken? I hate to go fill my CO2 tank up if I still have plenty in there...