My iPhone's home button will not work after a front panel replacement!

I was repairing an iPhone 4S for a client, when I accidentally tore the digitiser cable. I replaced it with a new screen and so a new home button to match the colour (black). When I reassembled it, all was well, but the home button was not responding at all. I took it apart several times to look at it, I replaced the home button with one out of a donor phone, I did the same with the dock connector assembly. It still doesn't work. I tried to use the apple recommended home button calibration, but that did not work. It is running iOS7. Any help would be greatly appreciated! Thanks in advance :)