I had some issues after replacing this cable.
Once I had it in and back together only the down volume was working, and shortly after the gyro gave out.
I ended up going to where the new cable connects to the board, removing it, then replacing it as gently as possible. Not too firm.
I also removed a foam spacer in that area because it was pushed out over the gyro board.
Now I'm back to full functionality!
What you need is the little orange circle with a black dot. When I pulled out my button, I discovered the little black dot was missing from the orange circle. You can take apart your headset and find 3 of them. Or you can try and add a small piece of material into the current broken button actuator.
It would be better if Ifixit it sold a sheet of these little actuators, instead of selling everyone an extra iphone power button, that nobody needs.
It turns out you don't need a new button.