1)unscrew the tank
2) put a few drops of paintball or air tool oil into the ASA where you screw the tank in
3) screw the tank back in tightly; it could be an issue that the tank is not screwed in enough
4) fire away and distribute the lubrication throughout the marker.
If it's still not working, you may just be out of CO2
Did it work before?
You screwed with it, didn't you?
Got what you deserve.