To anyone who's wondering, I have everything fixed now. The sound slider works perfectly. When i opened it up the outside slider moved the inside slider just fine, and when I turned on the the 3ds(the the back open, and the guts still showing) everything worked fine. When i put everything back together though it stopped working again. I opened it multiple times and it kept doing the same thing. Eventually i went to open up the back again but kept the 3ds on the whole time as a test. When unscrewing the screw closest to the sound slider it just worked. For whatever reason, having that one screw to tight broke the sound slider, not sure why, but i just left that a little more lose and everything is fixed.