Beergas tank broken?

[GRBC]

I have a 5b tank of N/CO2 that I have been using to push beer through a stout faucet. I can feel that the tank is too heavy to be empty, but when I take off the regulator and open the valve nothing comes out? I left it out of my kegerator overnight to make sure that something wasn't frozen, and still nothing. Any ideas?

 

[zazbnf]

It is empty, beer gas is not in a liquid state, the tank will weigh almost exactly the same full or empty. 5lbs of beer gas won't go too far.