If the Xbox sync button is not working, replace the controller batteries first and see. This article lists some fixes that will help you.

If Xbox One Controller is not recognized, not turning on, connecting, or showing up, check the USB cable and replace its batteries. Here are some other working fixes.

The ability to decide which buttons do what on your controller should always be entirely up to you, so Microsoft has made sure you remap them however you'd like.

The notorious Xbox Elite controller bumpers can and do fail, but there's a real easy fix.