Yes, you hold the Powermax can upright to get liquid in UNLESS, as grbaker said, the tube has fallen off inside the can (that may be what you can hear rattling around inside the can). If that happens (it does sometimes), then you'll have to hold that can upside down to get liquid out. Also, if the on-board can is filled with gas, it can have enough pressure in it to keep much liquid from getting in.

To fill the on-board tank, first release the pressure and let it empty. This can take a few seconds as the can will cool as it empties and you have to wait for all of the liquid to turn to gas and get out of there. Warming it up with you hand if you can get to it can help. Then close the release valve and fill with Powermax. When you connect the Powermax can, make SURE that liquid starts to flow immediately into the on-board tank or you'll just fill it with gas again and you'll have to empty it again. Keep the Powermax connected and either upright, or inverted, as required for liquid to flow - until the bubbles just stop flowing into the on-board tank. This should insure that the on-board tank has enough liquid in it to start the engine. if you don't get enough liquid in the on-board tank, it will run out quite quickly and the engine won't start. In fact, it may not even light off in the first place. I think that is probably what you are seeing.

Of course, another question is are you sure that the solenoid is hooked up correctly (there is a flow direction for it), and its actually working?

Bob