Geeetech

I have a Prusa I3 Mendel Reprap from Geetech built from kit, with Arduino Mega, Ramps 1.4, A4988. I have had it only 1 month. the LCD2004 display stopped working. It was working fine, but ow it is just blank. The light comes on, but no characters. I tried pushing the reset button, but it does not do anything. I checked the wiring it is all correct. What is wrong? Is the display defective?

There is a adjustable resistance on the back of LCD board, screw it and see if something happen in the LCD.