No power and not able to turn on

Hi All

New here, would appreciate any advice.

My MacBook 2015 ( I know is now old but I happen to love the machine ) keyboard stopped working so I bought a new keyboard ribbon cable. I fit this cable and ever since then my MacBook wont power on.

When I open it up with power plugged into it, the LED on the MLB opposite side to the battery disconnect button, starts dim then gets brighter in 3 stages then returns to being dim and it just keeps doing this.

I tried the unplug of the USB C, disconnect the battery (Press the button) and then press and hold the power button for 5 seconds, this did nothing.

I bought a second user MLB thinking that I had bricked it, but this does the exact same thing so I can only deduce thet either the trackpad (or the trackpad to keyboard ribbon cable) is bad or I am just extremely unlucky and purchased another dead board.

I am trying to work out exactly where on the face up side of the board (when its in the chassis) the power on pads on to see if I can jump it and if it powers on, then Ill know that the trackpad or cable is faulty.

I hope someone could help :) Thank you in advance.