Why is my r2 button not working

Dont know of this helps or not but…. If your controllers get dropped regularly, like mine do…..take it apart, carefully clean the contacts of the conductive film and it's respective contacts on the circuit board. I use 90%+ isopropyl alcohol and a few Q-tips. Scrub, but carefully. Then use a clean cloth to buff the film contacts and the board contacts. Make sure everything aligns correctly when you screw the circuit board back down. Screw the circuit board back down and connect the battery and try it out. Unless your controller is physically broken, or the rubber pads are torn or crushed, this should fix your problem. Unless it was submerged in fluids, just smashed to !&&*, or a button was physically broken from being to rough….this had fixed every single one I've come across with a “shoulder buttons worked and now they don't “ scenario. It's almost always that film. It moves and that was a design flaw.