There are a few small ribbon cable connectors on your 3DS XL motherboard that you need to be very careful with. The one that connects the circle pad is ZIF (zero insertion force) connector, in which you lift a lock that allows you to gently pull the ribbon cable out. Look at it carefully with a magnifying glass and study it. Compare it to the other connectors. The solid black ones are NOT ZIF connectors and if you attempt to lift the "lock" (which is not a lock) you will permanently damage the connector.