I've the same problem with my Macbook pro.

In the beginning I thought the screen wasn´t compatible, so I tried with the old one, but it didn't backlight nether (I did backlight before replacement). Hence I resolved something else was damaged during the replacement.

LED screens don´t need an inverter, backlight leds are directly feed from the motherboard thru the flex cable. I tested the cable and it´s ok, the motherboard isn’t giving voltage for feeding the leds.

There is motherboard damage and I don’t know how to fix it, comments will be appreciated.