Chosen Solution
I recently replaced my screen in my iPhone 5S. Once the screen was replaced everything seemed to work fine. After powering off the phone I was not able to power it back on. I have to open the phone back up, and disconnect then reconnect the battery before the phone will power back up. The latest iOS is running on the phone.
I’ve noticed this twice now, both times with iPhone 6 display assemblies. Both from iFixit. It’s kind of confusing, because I’ve never seen anything like this. But at the same time, these things do happen, when installing parts. First try the original part, make sure that it’s in good working order. Then see if you can get a replacement part, from where you got the new/current part
I have seen this issue before when using a non-Oem LCD. I would try plugging in your old screen to see if your new part is not playing nice. If your old screen works, I would make sure your new screen is an OEM LCD and not a “high quality” like sharp, lg, etc.
