Methord-1;
Reset the System Management Controller to Fix-
1. Shut down Mac and connect it to your MagSafe adapter and a wall outlet as usual.
2. Hold down the Shift+Control+Option+Power button for a few seconds at the same time.
3. Release, then boot the Mac as usual
Method-2:
Try a Keypress Sequence to Fix-
1. Press the Power / OFF button once – this will bring up the dialog box which you can’t see
2. Press the “S” button – this is the shortcut to sleep the Mac
3. Hold down the Power button until a hard shut down is forced
4. Wait about 15 seconds, then hit the Power button again to turn it back on.
Hope this might help you.