Need some help, folks.

I recently replaced the screen on my N9 because it was cracked. Everything went fine until it came to turning on my phone. Usually there's a brief vibrate when it turns on, and that was the case with the cracked screen too, but not with the new one. No vibrate, the screen doesn't light up, and the corner LED stays on for about 5 seconds before dying.

I got the new screen from parts4repair.com, which a lot of the other people here recommended, so I'm hoping I didn't get a dud. Anything else I might have missed? The proximity sensor was placed just fine. The issue is that the phone won't turn on with the new screen.