MacBook screen dims and the machine goes to sleep after a system boot

About 3 months ago, I opened my macbook in order to change its Thermal paste, however something went wrong and the screen just would become very dim (even though the brightness is 100%) and the machine after a few seconds goes to sleep

Though just about now, I found out that there may be some problems with a main ribbon cable that connects a keyboard and touchpad to a motherboard, because when I disconnect it from the Logic board the screen comes back to normal and the machine works just fine. What do I do in this case ?

I guess now I know that it’s a hardware issue and not a software one, cause I restored the system like 5 times and no results. So, now i’ve got this problem, and need some help to get rid of it.

Thanks in advance