Check these functions, but it may need a total reset from the
software.
LModeBAT
Sets the backlight mode to On, Stealth, Normal, Key, or Ignore
when operating under battery power.
LModeEXT
Sets the backlight mode to On, Stealth, Normal, Key, or Ignore
when operating under external power.
LiteArea
Controls whether the LCD, keypad or both should be illuminated
when the backlight is active.
LiteTime
Controls the amount of time the backlight stays on.
LiteLevel
Controls the brightness of the backlight and the Alert LED
You could also try updating the CPU Firmware from the EZ Scan Digital program - Updates pull down menu.