No onboard video after SSD upgrade

I have no video after upgrading to an SSD on my 2010 iMac 21.5

It boots just fine on an external monitor which seems to indicate that the video card and system board are not the culprits.

I did notice that the LVDS cable was missing pins, so I ordered a new one. Still no joy.

The LCD panel does not appear to be getting any power. When I shine a flash light on it, with the machine turned on of course, I get no ghost image. The onboard display is not detected by the OS.

This seems to hint that I have:

A damaged display port socket on the video board OR a damaged inverter OR a damaged LCD panel.

There is no visible damage to the port. It still seems to be firmly attached to the board, and the new LVDS cable slides in with no resistance.

I have been very careful with the LCD panel. I've taken this thing apart and checked the cabling three times now.

As I think about this it seems to me that, because the OS doesn't detect the onboard display, it is likely that this is a cable issue.

Does anyone know if the back light only triggers if a connection is established with the LCD?