I believe one cable is for the LCD and the other cable is for the SD Memory card. I kind of doubt it is a cabling issue, but given the two functions are on separate cables, it is worth checking. Also, doesn't the Rumba have an SD Memory card slot on the board? If so, you should focus on getting that to work first because they will share a lot of signals. If you can get it working on the Rumba, you have a better chance of getting it to work on the LCD Panel.