I had exactly the same problem. I persisted and found that, after the connectors were properly seated, I had to 1) completely install the screen, including the screws and 2) perform an iPhone reset. To perform the reset, hold the wake/sleep button (on the top) while at the same time holding the home button (on the screen). Hold them until the apple logo is displayed on the screen (approximately 10 seconds). After the apple logo came on the screen, everything was look'n good! I hope this works for you; i was bummed, not becuase i would have had to spend another $99 but because ATT automatically extends one's contract every time one buys a new iPhone, even if it's a replacement. Good luck!
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