I agree about the pucks. I assume the model is a CL-200? These things have notoriously bad metering and I only use mine when I need to use pucks to add CYA, then I run it full open. In fact just checked mine and the metering doesn't seem to work at all but water flows so I don't care. Try this. With pump off, take off the lid and water should drain out of the chlorinator housing into the returns. Just place the lid on, don't screw it down, and turn on the pump. Putting the lid on as a cover is just a safety measure if the thing squirts and splashes out or shoots a stream straight up. Once the pump is on you can take the lid off, carefully, to observe the water level. Water will come out of the tube that's about 4" or so off the bottom on the side opposite the metering control. Should see the thing filling slowly at a low setting, faster at a high setting. I THINK. As I said, mine always flows. If it fills and drains then it is at least working to some degree.
Best I can do.
Al
BTW: Pucks don't go bad if you keep them dry and in a container that's at least somewhat well sealed.