Tippmann_A5

My PIRANHA one day just stoped working on C02 i tried different tanks on different days, C02 just doesnt work, then it works fine on HPA what could be causing this? I dont have a reg just a gas thru grip, you would think if there was a leak HPA wouldnt work either so it cant be leaking, what can be wrong with it? I could really use anyone who is knowledgeable to help me plz.