I have an Arduino UNO and a 16x2 LCD Shield that have been lying unused for one year, or perhaps more. Yesterday I connected the Arduino via USB, uploaded a couple of simple sketches, played around with the LED and button bricks and everything seemed to be working fine. Then I tried to connect the LCD, but it wouldn't work. I eventually adjusted the potentiometer until one row had solid white squares on it and the other did not, with the backlight lit.
I tried both connecting the shield directly on top, or separately using wires and wiring up the +5V, GND and 12, 11, 5, 4, 3, 2 pins. I also checked the wires and the pins using digitalWrite and digitalRead. The problem doesn't seem to be there. No matter what I try I cannot get it to display anything else other than squares.
I have tried using different pins and changed the LiquidCrystal initialization accordingly, I have also tried the I2C Scanner and it just kept reporting that no LCD was found (with the shield mounted and lit).
I have no idea what to do next or how to determine whether the LCD panel controller is broken or not.