blank black screen with file and question mark symbol

Folder with a question mark

If you see a folder with a question mark appear instead of the Apple logo, it means your Mac couldn't find a local or network-based startup disk. This can happen if the disk selected in the Startup Disk pane of System Preferences isn't available. Wait a few seconds to see if your Mac is able to locate the startup disk you specified.

If you still see a question mark after waiting a few seconds, use Startup Manager to start up your Mac, then select your startup disk from System Preferences.

If a question mark appears after you install a software update, select your startup disk again using macOS Recovery.

1. Disconnect all USB cables and USB devices from the Mac, aside from a mouse or keyboard if applicable
2. Shutdown the Mac
3. Reset SMC
4. Reset NVRAM/PRAM
5. Boot in Safe Mode - Hold down Shift key at startup until you see progress bar then let to.

Check under “About this Mac” to see if your install of High Sierra completed. If not....

Disable any startup items in System Preferences > Users & Groups > Login items as well as any anti-virus apps you may have, and then restart your Mac.

Look in Applications for Install macOS High Sierra. You might need to download the installer again. You’ll need to restart the macOS High Sierra installation process again.

If this fails....use the second option to upgrade to High Sierra after running First Aid in Disk Utility in Recovery Drive.

• command R to reinstall the latest macOS that was installed on your Mac, without upgrading to a later version

• option command R to upgrade to the latest macOS that is compatible with your Mac

• shift option command R to reinstall the macOS that came with your Mac, or the version closest to it that is still available

See these articles macOS Sierra: If a flashing question mark appears

If a flashing question mark appears when you start your Mac - Apple Support