1. Reinstall the toner cartridge with the middle cover closed [A] to make sure that the shutter is properly lifted.
  2. Open the middle cover and make sure that the toner cartridge gear [A] and the middle cover gear [B] are engaged.
    (Left: not engaged, Right: engaged)
  3. Eliminate the toner clogging in the supply port of the toner cartridge, shake the toner well, and then reinstall the cartridge.
  4. If the problem persists even after performing Steps 1 and 2, replace both the PCDU and the toner cartridge.