My message error was sepcific for magenta after I removed it to refill it. After refilling, cleaning metal contact points, resetting the metal tab which prevents message of "low toner", I put the cartridge back in and received the "magenta toner not installed" message. I turned off the printer (safety first!) , I then pushed the button left of the hole where you slide the cartridge in, There is a squarish hole with a circular or cynlinder shaped button in that squarish hole. Use a small screw driver to push and hold it in. While the button is held in I gently rotated the cartridges so that my magenta cartridge was no longer in view, (rotate them counter clockwise). I released the button, shut the door, then turned on the printer.