What is happening here is the phone has maintained a relationship with your original display. Since the battery had not been disconnected and reconnected after the new display was installed, the new display appears black but the phone will boot up just fine once the original display has been reinstalled, so your phone behaves as though the display has never been replaced. The fix that is most common is present in the replacement guide for this display. The battery must be disconnected and reconnected after the new display has been installed.
If that does not help then please try the following (even if you have done some of them already):
1. To start with, I would recommend doing a .
- A DFU restore will update the OS, and give you a clean slate to further troubleshoot the device
2. If the DFU restore doesn't fix the issue, I then recommend inspecting the digitizer and LCD cables for damage.
- The cables are fragile and can be damaged during reassembly. e.g., slight tear, pinched cable, damaged pin, etc.
3. Clean the contacts and cables
- Clean the contacts gently with isopropyl alcohol/rubbing alcohol/surgical spirits
- Use a Q-tip or soft bristled brush
4. Reinstall the display assembly.
- Keep in mind that connectors can become loose or dislodge completely during reassembly, which can easily cause the display to not turn on.