That should not happen if the hardware is OK. So,
Fix Sierra Installation
Try each of these in order. Test to see if the computer is working properly:
- Reset the PRAM
- Reset the System Management Controller (SMC)
- Start the computer in Safe Mode, then restart normally. This is slower than a standard startup.
- Repair the disk by booting the from the Recovery HD. Immediately after the chime hold down the Command and R keys until the Utility Menu appears. Choose Disk Utility and click on the Continue button. Select the indented (usually, Macintosh HD) volumeentry from the the side list. Click on the First Aid button in the toolbar. Wait for the Done button to appear. Quit Disk Utility and returnto the Utility Menu. Restart the computer from the Apple Menu.
- Reinstall OS X by booting from the Recovery HD using the Command and R keys. When the Utility Menu appears select Reinstall OS X then click on the Continue button.
If the above does not help, then:
Install Sierra from Scratch
Backup if possible before continuing.
- Restart the computer. Immediately after the chime hold down the Command and Rkeys until the Apple logo appears. When the Utility Menu appears:
- Select Disk Utility from the Utility Menu and click on Continue button.
- When Disk Utility loads select the volume (indented entry, usually Macintosh HD) from the Device list.
- Click on the Erase icon in Disk Utility's main window. A panel will drop down.
- Set the Format type to Mac OS Extended (Journaled.)
- Click on the Apply button, then wait for the Done button to activate and click on it.
- Quit Disk Utility and return to the Utility Menu.
- Select Reinstall OS X and click on the Continue button.
