Please do try the following troubleshooting steps that might help in resolving that issue.
- Remove the battery and AC adapter then press and hold the power button for 20 seconds. Plug just the AC adapter and turn it back on, if your laptop boots up normally you can reconnect the battery as well.
- If it still won't boot up but there are lights indicating it's on connect and external monitor into your laptop and see if you'll get any display from it because if your do that means there's something wrong either with the display or the cable connecting it to the motherboard.
- Lastly, reseat the RAM. Take them off then put them back in after couple of seconds making sure that they are all seated properly in each memory slots.