Screen not working after replacemnt

I recently replaced the lcd on my iPhone 6 plus and it does not work. At first i thought it wasn't working because of the phone being dead so i left it on the charger over night. The next morning i tried powering it on and nothing happened. I did all resets and the phone screen was still black as if the phone was dead. When i connected the phone to my laptop itunes recognized it. I put my old screen back on and it worked perfectly but the replacement screen does not.