I think the leak is a possibility check to see if your bottle is still full.
If you have CO 2 in the bottle then somehow it's not getting into the keg.
If the pick up tube being clogged were the problem, the beer that did come out wouldn't be flat.
Start by checking the bottle, if you have gas in the bottle pull the pressure relief on the keg. if there isn't any pressure in a keg, somehow the gas isn't making it to the keg.
Start checking the regulator. Make sure the valve on the tank is all the way open, the pressure is set where you want it and the valve after the regulator is open.
After you check all that post your results.