Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
Hold down the Power button for 5-10 seconds and this will turn off your Mac. Then turn it back on and see if it works. If not, then follow the troubleshooting steps below please.
First reset the System Management Controller of your Mac. Follow the steps below;
Shut down the computer by holding down Power button for 5-10 seconds.
Plug in the MagSafe power adapter to a power source, connecting it to the Mac if not already connected.
On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
Release all the keys and the power button at the same time.
Press the power button to turn on the computer.
If that didn't work, then reset the PRAM and NVRAM of your Mac. Follow the steps below;
Shut down your Mac
Restart and immediately hold down Command-Option-P-R keys at the same time
Hold the keys down until the computer restarts and you hear the startup sound for two or three times.
Release the keys and let the Mac bootup.
Please let me know if that didn't work, so we can continue troubleshooting.