Yoga 700 14-ISK No display

I've been having flickering display because its LCD cable was defective. I have confirmed this with a local repair shop, but just I had to fix it on my own cause I moved to other city. Anyway, I ordered a new cable and tried to replace it yesterday. Now I only get black screen when I turn on my laptop.

Before I replaced the cable, the display kinda worked. It just had the pretty bad flickering issue. When I opend the back part of the display, the whole white board (I think it's a digitizer) had light on when I turn on my laptop. Now an obvious issue is, it doesn't have light on after I replaced the cable. I tried with the old cable and had no light on it...

I didn't really touch anything on the motherboard other than the part connecting the cable. I also troubleshooted battery, A.C adapter, hard drive, fan, Ram. I double checked if there is any loose connection on the motherboard. I left the laptop overnight with battery removed so that cmos get reseated. Nothing worked so far.

I have connected the laptop to an external monitor and it didn't work. I'm not sure if it totally doesn't work cause the setting for switching to the external monitor was quite tricky without display on in the past and I had to tried it for a few days to finally get it worked.

The conclusion of the troubleshoot instruction is that the problem lies on the motherboard. But everything including display itself was fine, it was just the cable. I carefully treated every part and I think I didn't really break anything on the matherboard. What should I do now?