TriggerFinger

do you have a laptop battery (with some charge)? try that without the AC adapter. that will help tell if it is a DC jack connector problem.

if battery is already present, remove the battery and run on AC only.

if your battery is not charged, try another good/working battery from a similar laptop (borrow one from a friend or colleague).

last thing is open the laptop up, remove everything and put them back one by one, also reseat the cables making sure they are connected securely, powering up each time you connect a device or component. obviously it will not boot normally, the objective here is to see if power would go in and (to the very least) light up some LEDs or show any sign of life.