MacBook doesn't turn on pressing the button

But the mac charges fine. The battery goes up to 100% and it works when unplugged

@Giacomo Zema The full name of the circuitry is "PBus supply and battery charger" to be precise. It consists of a number of components and needs the aid of SMC to work properly. Unless there's a major fault shutting down the full circuitry, it may happen that parts still work fine while others stop working, as it seems to be the case with your Mac. Whether the issue is caused by the SMC or by another component on "PBus supply and battery charger" or sensing, as more often happens, it can't be figured out without thorough testing.

Ok I think it might be it. The keyboard is not faulty since when i press the power button when the computer is on it registers it. The problem occurs when it is switched off. So I figure it is that part of the circuitry that is involved. How can I investigate further? Should I take it apart? Inspect the motherboard? I already took the bottom cover off and did not notice any inconsistency on the logic board

@Giacomo Zema A visual inspection would be a good idea to start with, better with the help of a good light source and some magnification. Then I'd check all the SMC_ONOFF_L circuitry and then jump to PBus supply and battery charger and finally the SMC itself.