Phone not working after screen replacement

So, I have recently replaced the screen on an iphone 5 after it was pretty well pulverized. This is not my first rodeo. I have replaced about 4-5 iphone 4 screens, 3 iphone 5c screens, and one other iphone 5 screen.

I replaced the iphone 5 screen with a cheapo one that came over on the slow boat, and while I had the phone open I went ahead and replaced the lock/volume buttons, since the lock button was on its way out. Before completely reinstalling the screen onto the phone (only the ribbon cables connected) I tried powering the phone on. I got the low battery screen. Great, the phone is working. I proceeded to reinstall the screen, and it was a very tight and bad fit.. I kinda had to push a little harder than I normally would had had to. Once I had the screen installed, I attempted to power on the phone, and nothing. So without much thought, i figured it was the fact that I bought a very cheap screen, and I probably messed it up while trying to get it in. I've had this happen before. So I proceeded to order another screen from a more reputable seller, and installed it. I have the same issue of the phone not turning on or displaying anything.. It does not vibrate or make any noise when I plug it into a charger, and it does not seem to be detected by a computer (though I have the screen off again at the moment.

Any thoughts?