It does not appear that water is entering the heating chamber. Chamber gets very warm, but never produces steam. I unplugged, and shaking it, could not hear water sloshing in the heating chamber. The long, slender cartridge/cylinder that is inside the water bowl appears to have a dark substance inside, is this a clog and should it be replaced? Depressing the push/release button shows the unit has AC as the outside plastic casing gets pretty warm, but does not make any kind of noise or hiss sound from steam. Any suggestions?