LCD does not work correctly after replacement (no backlight)

Hi, I changed my surface pro 2 lcd screen, and after the replacement, the backlight didn't work, I can see the login screen dimmed in it.

I bought the lcd flex cable in case it was broken, I have tried 3 different cables, and two different lcd screens, and neither of those work.

I don't see any damage around the connectors on the board, and can't figure out what is the problem here.

Any ideas?

Edit:

I connected it to a external screen and the surface screen appears in the device manager as Digital Flat Panel (1024x768 60Hz)