IPhone 4 Home button not working? - 1

I've received a iPhone which has been dropped and stopped working. I've fixed most of the things and its working fine now. I've replaced the dock connector and the home button but the home button still doesn't work. I've tried with 2 brand new dock connector and two home buttons but still doesn't work.currently i'm using assistive touch. Any idea how to fix? Please Help. Thank you

Added (1). I've also fully restored the phone to iOS 6.0.1. Still not working?

Added (2). I've re calibrated the home button and its a brand new one, dock connector is also brand new. So what could be the problem?

1) Calibrate your Home Button
- Open up a stock app (like Clock) hold down the sleep button until you see " Slide to Power Off", when you see this let go of the power button and hold down the home button, after about 5- 10 seconds the app will close

2) Realign the Docking Port
-Plug a USB Cable into your iPhone, then gently press down on the connector so it'll push up on the home button. When you apply pressure, click the Home button, remove the cable and see if your problem is fixed

3) Clean the Home Button
- Pour 2-3 Drops of Rubbing Alcohol directly onto the home button, then using the eraser end of a pencil tap onto the Home button to cause the alcohol to seep into the button and remove all the sticky residue that could have built up causing the button to become unresponsive. Wait 5- 10 minutes then check to see if your Home Button is back to working again.