Touch not working even after replace with new screen for iPhone 4

I do replace screens lot times so i am not bigginer.

I have a iphone 4 gsm usa at&t model, suddenly not response to touch at all. so i think touch connector might be loose. but it was good connected. so i try to replace new screen but when i connect new screen with same iphone. it still not working. I try to use both screen to other iphone and both screen working good.

So what i understand is problem is motherboard bcoz charging port also looks good to me and iphone is not water damage.

is any body know solution. iphone is not in warranty.

I done restone in itunes. i done pressing both button trick so many times. but not working