Hello,
It sounds like you are not making the connection between the carto and the battery. One of two things could be happening. First, I would carefully unscrew the bottom to be sure that the part that makes the connection to the battery is properly installed. I know, it is a little different set-up from the protank II. When you put the head down into the piece that ties it all together try to screw it on, mine turns a couple of times and seems to tighten it up, then put it back onto the
tank part and try it on the battery again.
Second, the pin on the center of the battery may have been pushed down a little. So you can gently try to pull it back up, but do not yank it. Take a pair of tweezers and gently rocked it a little to see if you can lift it. DO NOT PULL or it can come out and you may not be able to get it back in/or the wiring may come undone.
Give the first a try. It took me a couple of times too. No need to empty the tank if you have a holder to place the tank upside down where it won't spill.
Let us know.
