Top Case Replacement Keyboard/trackpad not wokring

Hello G@ys.

So I bought an used top/upper case replacement for my macbook pro m1 A2338 and for some reason after doing all the steps (youtube video) The macbook turns on just fine, the screen works but the Keyboard, Trackpad and Touchbar does not work. I plugged an external keyboard and mouse and I was able to login. Everything else seems to be working fine (Wifi, Bluetooth, Sound, etc). also the backlid of the keyboard turns on.

I went back and checked all of the cables and they all seem fine and securely connected. So my questions are:

1) What can have gone wrong?
2) I can't identify what are the cables for the Keyboard, Touch Bar. I believe the cable for the trackpad is the one directly above the battery, right?
3) Can this be an issue with the motherboard? Or is it a cable issue?

Any help and/or pointers would be greatly appreciated.

I can't find an upper case repair guide here in iFixit, if anyone now of a good guide please let me know.

Thanks.

Carlos Sosa