Replaced iPhone 5 battery and it does not power up, screen is black. It does get warm with charging but nothing else. Replacement went uneventfully, I did not remove the screen, as recommended in several posts to save time and angst, instead held it 90 degrees with a band around a glass jar to hold it in place. No cables appeared broken or disconnected (took off protective plate to inspect cables but did not remove them or the screen). Hard and soft resets unsuccessful. Any thoughts / ideas?