Why isn't the LCD displaying anything after replacement?

I got a surface pro to fix which had a devastated LCD. I bought a new LCD and fixed it and I found that the screen is fine but the back light does not work. I ordered a new backlight cable for the LCD. With the thought that every things gonna be fine, I fixed it and connected it to the LCD and the motherboard but now neither backlight nor the display works . It's completely dark and nothing works at all. The tactical feedback from the home button works fine as it did earlier but I can't see anything on the screen at all, no backlight and no display. A friend told me that by removing the battery it might give me some results, but the SurFace pros battery is some hassle to remove all I did was disconnected the power cable, I don't know the technical term for it but it has the " 12 V" written over it, from the motherboard just to see and yet it still does not work. Did anyone ever face such an issue ? Could anyone tell me what mistake did I do other than taking the responsibility to fix this tablet/laptop hybrid ? Can anyone tell me if there's a work around or anything to just get the LCD in a working condition without buying a new one ? Your answer is appreciated , thanks in advance !