Why is my right d-pad button not working?

In order to fix the Nintendo DSI D Pad, you must remove the screws from the bottom of the console, there are several outer screws, one inside the battery compartment (the far left hole, it's a big larger than the other 2), and there's a little black screw where the games insert.

Once you've removed all the screws, carefully take a flat edge and gently pull the shell open, take your flat edge and slowly and carefully run the flat edge down the separation until it pops loose.

Once you have the shell apart, gently open it, being very careful not to pull on the power connector (the little green board with the white connector and ribbon cable. The smaller green board has a few screws, take those off carefully, unplug the black connector that's attached to the board by carefully lifting it out of the shell and then gently flip the board over.

At this point, you should be looking at the bottom side of the Dpad, take the rubber insert out, clean it with a Qtip dipped lightly in alcohol. Once the rubber is cleaned, check to make sure there are no tears or defects on it, set it aside, and then using a pair of tweezers, pop the D pad button out, clean it just like you did the rubber piece.

Once done, put the D pad key back, replace the rubber and then before you hook everything back up, press on the silver buttons on the board itself, make sure they are clicking and making contact. If they are, reassemble the unit, pop in the battery, and test. You should be good to go.

IF you get it back together and it does not work, you have a few possibilities, either the ribbon cable is bad or not seated properly, or the power board is bad and needs to be replaced.