Why is my LCD not working after screen replacement? But backlight is.

it's possible the digitizer cable isn't connected properly, I'd say unhook the assembly and re-hook it. if that doesn't work, try unplugging the battery from the board, and plug it back in.

it's also possible (maybe?) that the digitizer cable got torn during assembly, and it's not always easy to see the tear as the smallest nick in the wrong place can cause it to go bad.

That is a common symptom of long screw damage. If the screws covering the connectors are put back in the wrong spot.

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iPhone 6 No Backlight after simple screen replacement:

An iPhone 6 comes in to a shop for what seems like a straightforward screen replacement. However, the new screen does not light up.

After component failure was ruled out, this phone found its way to my microscope.

I confirmed the phone was turning on, but showing no display--not even on an original iPhone 6 display. This seemed to be a straightforward backlight repair. Raise your hand if you know what component(s) should be replaced to solve a standard backlight failure in this situation? If you said "the coil" or "the backlight ic" punch yourself in the face and read Backlight 101.

Given the history, those of you who read Backlight 101 will recognize that this will most likely be connector damage or a bad backlight filter. I have repaired a backlight from a water damaged iPhone 6 before, so I'd already mapped the backlight filters.

I opened the phone and found very minor damage at the edge of the LCD connector, but all the pins intact. I believe the connector is okay. I uncovered the backlight filters and found that they showed no signs of damage, and had continuity as normal.

I even used my new FLIR One infrared camera to make a heat map comparing this iPhone 6 to a normal iPhone 6. Spot temperature measurements were largely the same. No hot spot, so therefore no short circuit.

Since the history tells us the display was working fine after the drop and before the screen change attempt, what could be the problem?

Making a connection to the recent BSOD problem on the iPhone 5S, I took a hard look inside the screw brackets. In a normal phone, the bottom of the screw bracket is nothing but the clean black coating of the solder mask applied to all non-conductive surfaces of the board. Sometimes you can see blue plastic along the edges of the screw bracket from the plastic coating on the shaft of the screws.