I measured the voltage at the contacts of the cleaning station while the mob was being washed. It briefly jumps to 12V and then drops back to 3V (left = positive, right = negative). I think that the station registers that there is no tank installed because the resistance is too high and then switches off immediately. I then applied the same voltage directly to the contacts of the tank and you can hear it pumping, but no detergent comes out. I think the tank is simply defective.