Display doesn't work after replacement

My Macbook air display was broken and I bought a new display assembly.

I've replaced with the new one, but nothing is shown in display.

I realized that I connected the display ribbon cable( on the top left at the logic board ) as wrong side... ( top and bottom were changed... )

I changed it correctly and turn on the Macbook, but it does not show anything only black screen.

There is no light on the apple logo.

If I turn on, the fan rotates well.

I've checked the back light fuse on the logic board with my tester, but it is not a problem.

Are the GPU or Display Ribbon Connector or something wrong?

Do you know what I have to do in order that the display works or in order to diagnose?