Hello guys, I would like to first thank iFixit for these amazing repair guides they have always worked for me! Thank you!.

When reassembling the phone make sure to put the screen from top to bottom, but be aware there are 2 small flaps on the top left side of the screen (you can notice them using another iphone as a flashlight) if you don't put these 2 flaps first then you are going to have a little space between the top part of the screen and the aluminum frame, at least this happened to me and then I inspected the screen using a flashlight and then I found these 2 tiny flaps behind the screen near the top left corner.

I hope it helps!