Please do try these troubleshooting steps that may help.
- Since the battery is built in, doing a hard reboot won't be possible.
- Unplug the AC adapter then try pressing and holding the power button until everything is off.
- If it will still just go into sleep mode, last option would be to open the back of your laptop to remove the battery to completely shutdown the laptop.
- Here's a video guide on how to disassemble the laptop: https/www.youtube.com/watch?v=PBb4WmV3uFE
- Once the battery is out, unplug the AC adapter as well then press and hold the power button for 20 seconds then put everything back together then try booting it up again.