Keyboard Backlight not working after topcase replacement

Hey,

So I've recently replaced my top case because it was in pretty bad condition. I bought a top case from ebay and took everything off of it and replaced the keyboard and trackpad from my top case. After disassembling and reassembling the macbook, the keyboard back light no longer functions. I took it apart again to check connections and everything seemed fine but still no backlight. Everything works fine, the fans, the ports, the keyboard, the screen and the ambient light sensor.

I'm not to concerned but I just wanted to see if anyone could help me out.

Thanks a bunch!