Define not working.
Does the button click?
Are you holding it in for a few seconds? and do the LEDs ever spin?
It's a common ground button and the trace goes straight to pin 48 of U6.
I'd also clean up those button contacts to make sure they are open, sometimes weird things will happen if buttons are held down or there is enough mess there to partially conduct when it shouldn't. The A button looks messed with also.
You can plug it into a 360 with the PnC cable and it will force sync the controller to the console. Might need to do that and it will straighten out afterward.