Unresponsive iPhone 5 after screen replacement

After replacing my broken iPhone 5 screen and digitizer and triple checking all my connections are correct the phone will not power on. If I plug it in to charge it I get a small vibration about every 5 seconds or so. I though maybe I got a defective screen so I tried to reconnect the old (broken but still working) screen and digitizer and I'm coming up with the same problem. Any help would be appreciated. Thanks