The black tabs on the floss cartridge need to be bent so that the cartridge fits all the way into the compartment. The bent tabs hold the cartridge firmly where it needs to be. It looks as though you didn't bent the tab nearest the wheel.
if the wheel isn't spinning you will in effect decrease the available surface area where beneficial bacteria can reside..causing the filter wheel to be less effective.Will it really affect the filtration ability of the filter if the wheel is not spinning?