Note: If your top or bottom screen was working before disassembly and doesn't work after reassembly, then it's likely that the connector is loose or dirty or damaged or not clipped or PLACED UPSIDE-DOWN. I had this issue with my Super3DS XL(2015) and it turns out that the reason why my top screen wasn't working after put together, was because I had the top LCD connector upside-down. After I correctly put the connector in, It worked again! :)