Check on [guide|596|this guide|page=3], look at the photo in step 17, and you will see a white disc in the bottom middle of the photo. That is the home button. Underneath the white disc is a gold ring. When the home button is pressed the disc pushes down and creates a circuit with the ring. I would gently pry of the white ring since it is only held in place by a weak glue lift it up and you will see a small metallic disc on the underside of the white disc. Clean both of those areas thoroughly with isopropyl alcohol.Then carefully align the white disc back over the gold ring and tape in place with just a small piece of sellotape. Hope this helps and good luck to you.