Try the following:

1. Turn off computer
2. Reboot Mac into Recovery (press and hold Command+R when you hear the chimes until a screen loads)
3. Select "Disk Utility" ![enter image description here][1]
4. Select your "Macintosh HD" volume on the left and press "Repair Disk Permissions" ![enter image description here][2]
5. Once that has finished, reboot your computer

If this doesn't work, call Apple Support [1]: https://i.sstatic.net/WTd8k.jpg [2]: https://i.sstatic.net/Ka2ZA.png

Try the following:

1. Turn off computer
2. Reboot Mac into Recovery (press and hold Command+R when you hear the chimes until a screen loads)
3. Select "Disk Utility"
4. Select your "Macintosh HD" volume on the left and press "Repair Disk Permissions"
5. Once that has finished, reboot your computer

If this doesn't work, call Apple Support