iphone 3gs replaced lcd, now white screen

I dropped and broke the screen and LCD of my iphone 3gs so I replaced the digitizer and the lcd and everything is back in place, but now a white screen is all that shows up. I've tried to press the home button and top button for 10 seconds but no apple logo comes out. What's wrong & what can I do to fix it??

Also, I've tried to unlock the phone to hear any clicking noise and no sound. But music DOES play and it does pop up in iTunes.

Software

Try to replace full software with complete flashing remember with updated files.
That may be the way for your iphone's problem