Using Arduino Due with Adafruit RGB LCD Shield Kit

Hello,

I'm trying to use an RGB LCD shield with my Arduino Due. I implemented and tested the code on an Arduino Uno and it was successful. When I attempted to connect it to the Arduino Due it was unsuccessful and I'm not too sure why. The back light did not work and I could not see any code. The screen is on but that's about it without.

I connected it to the 5V and ground, as well as Digital Pin 20 (SDA) and Digital Pin 21 (SLA) and still nothing.

I also uploaded the newest library in the Arduino as suggested and no success. Any suggestions?