Please do try these troubleshooting steps that may help.
- First is to do a hard reboot, remove the battery an unplug the AC adapter then press and hold the power button for 20 seconds then try booting it up again.
- If it will still not boot up, remove the battery off the laptop then connect just the AC adapter and see if it will boot up or not.
- Do also try a different AC adapter that has the same voltage.
- Next to try is to reseat the RAM's, remove then all for couple of seconds then put them back in making sure everything is seated properly.
- Do also test each RAM's stick one at a time chances 1 RAM stick is just faulty.
- Another test would be to connect an external monitor and see if you'll get any display from it or not.
- And if all these will not work that means the motherboard is the problem already.