HOT Magnum Canister Help Please

I'm trying to set up my new HOT Magnum Canister and can't figure out what I'm doing wrong. I followed the set up directions very carefully and have gone through the whole process (disassembling and reassembling according to directions) several times and each time it pumps out the water that I put in the canister just fine but there isn't any water going in the intake so as soon as that water's gone it runs dry. As far as I can tell there's no suction happening at all with the intake. Anyone have this problem and have any ideas how to fix it? Thanks in advance! :help:

Thanks for the responses. edh - That was exactly the problem! I never would have figured that out in a million years so thanks for your help. It's now up and running perfectly. It took a little bit longer than I expected (about half an hour) for it to stop spitting bubbles and making noise but now it's running just fine. Thanks again!