There are several reasons that could cause the auto threader not to work.

• The needle was not raised. Press the needle position button.
  The thread cassette indicator will light up in green.
  
  
• The needle is not installed correctly.
  Install the needle making sure the flat side is facing the back.
  
  
• The thread cartridge is not threaded correctly.
  Make sure the thread cartridge is threaded according to the diagram.

Please refer to "Upper threading" of "Preparation" category.