The message (Cooling Down) indicates that an obstacle is in front of the exhaust outlet (ventilation hole) or the trouble occurred to the fan.
Make sure that you can hear the fan in the machine spinning and that the exhaust outlet (ventilation hole) is not blocked by something.

• Case 1: Fan is spinning.
  If the fan is spinning, remove any obstacles that surround the exhaust outlet (ventilation hole), and then leave the machine turned on but do not use it for several minutes.
   
• Case 2: Fan is not spinning.
  If the fan is not spinning, disconnect the machine from the power for several minutes, then reconnect it.