New replacement screen doesn't come on
I have replaced many iphone screens but I have a problem that I have never ran into before. The phone worked fine with the broken screen, but when you install the new screen, it doesn't come on when you power on the phone. But if I turn the phone on with the old lcd and then put the new lcd, it works good, however, if I turn the phone off, it will not come back on, until I put the old lcd back and turn it on that way. Help anyone please?!!