This part almost killed me. In the video, they’ve already loosened the adhesive so she pops it right off. The hair dryer should be set to hot and low blowing. It’ll take a few minutes & a few tries) to loosen the adhesive. I aimed at all sides of the cable (ie at both ends where the cable meets the case & straight on at the circuit board). To finally get it off, I mixed up using a spudger to play with it and a very fine tweezer to finally get a good enough grip to pull the button assembly off.
It is crucial that you make sure that the little black plastic bracket around the ambient light sensor is removed with it when lifting it out of the recess. It is very easy to not notice that it stayed in the recess and really difficult to make out any difference between the removed cable and the replacement cable. It took me a few tries to realize that the bracket was still in place and was why I couldn’t seat the replacement cable properly.
When putting everything back together, I took care of steps 10-12 (or, more accurately 12-10) after reinserting the SIM (so between steps 20 & 19). It was easier to do before dealing with reconnecting the screen.