and the pump is plugged in right? i would leave that black cap on and just twist the white cap.. keep that above the tank water... one last try. take the black sponge off the pump and let it run...
I would take the motor part apart and reassemble it and see if that will work. They have a help email address. I think you are going to have to contact them and ask some questions.
From the looks of it I have the same hob fuge. The airline should be connected like this. (The sponge is off in this picture) The other end of the line needs to be out of the water. Hope this helps