Hello,
The MB2720, will only slide the ink to the changing position when it detects that the ink is low or empty. If the ink tank is not sliding over, it will usually mean there is a problem detecting the ink level or the tank is full and there is a different reason the black ink is not printing. In this situation, you can try performing deep cleanings to unclog any nozzles or get the ink flowing again. If the level for the ink has a question mark or if performing the deep cleaning did not drop the ink level so you can change the tank or unclog the nozzles, it looks like the printer needs service. In this situation, I would suggest contacting support over the phone at 1-800-652-2666 or via chat from your MyCanon account.
