Why is my laptop’s power button not working?

Check the power cord:
Make sure the the power cord is plugged in securely and firmly to your laptop and the power adapter.
Try to start it up again:
Disconnect and then reconnect the power cord, and try to start up your laptop again.
Check the battery:
If your laptop is running on battery power, make sure the battery has clouded up.
Check the power settings:
Go to its Settings and navigate to the Power & Sleep tab. Change the settings to wake the laptop up when you press the power button.
Try restarting your system:
Restart your laptop completely and then try to press the power button again.