No power, No signs of life

Hi everyone, Over the last few years I have dedicated time to fix this laptop. My initial problem started with a few keys not registering when pressed (ex. When I press the "x" key nothing would show up). I have researched for a new component being the whole keyboard assembly. I have switched over all parts from the old laptop to the new assembly. To no prevail, the laptop tried to boot then shut off completely. No life in LCD or hardware signs just a power led indicator then turns off. I figured I might have damaged the old Display Cable via reassembly. I have bought a new factory cable and yet no provail yet again... I have just recently replaced the SSD and the CMOS Battery..

Update: I have no power in the device now I used a multimeter to check incoming voltage it was around 9-11v. No life now when plugged in, No LED sign, Not even a flicker in the screen.. Just dead.

I have ran out of ideas on what to do now.. Any key ideas will help deeply.