The toner cartridge is missing or is installed incorrectly.
Install or reseat the toner cartridge.

   Open the side cover.

   Open the front cover.

   Remove the new toner cartridge from its bag.

   Thoroughly roll the new cartridge five or six times to distribute the toner evenly inside the cartridge.

   Pull out the protecting film in the cartridges.

   Hold the new toner cartridge by the handle and slide the new toner cartridge in until it locks in place.

   Close the front cover, then the side cover. Make sure that the cover is securely latched and then turn the machine on.