Unfortunately, the thing the technician said to you is most probably correct – the motherboard of the laptop has failed and needs replacement. Nevertheless, you could try one last thing.
Pull the charger and the battery out from the laptop. Then press the power button and wait for about 30 secs. After that, try to boot the laptop with only the charger plugged in.
If nothing changes and the warranty of your laptop has expired I suggest you to take out the hard drive and try to connect it to another computer through SATA-USB cable. If your hard drive spins up on a different computer and it is recognized there, but cannot power up on your laptop, then the problem is hiding probably in the power supply unit on your motherboard. While on another PC, I suggest you to make a backup of your files, because in case of a MB replacement, you would need to reinstall the operating system once again.