I have replace the shell of our nintendo lite and now the top screen isn't working. Any ideas why?

Any ideas why the top screen of the nintendo lite isn't working after I replaced the housing?

The ribbon cable from the top screen is probably not plugged in correctly. It's a bit tricky. It took me several attempts to get it right when I fixed mine. Take it apart, unplug the cable, and put it in again. This time, make sure that it's in all the way and not skewed or upside-down. It's a good idea to insert a battery and test it before you screw the case back on.