The machine is turned on for the first time, the display is on and the light panel is not on? Starting the machine for the first time, the display panel is not on? Why does the Display screen is blank and no text is displayed? Why the machine can't read SD card content? Why, After the SD card is inserted, the display screen operation is delayed? During the auto-home the resistance of z-axis to rise is too large, and doesn't rise up?