If your Mac starts up to a question mark

..larrmak:

Second part, within above reference article, would generally work to resolve this issue.

If not; logical conclusion imparts suggestion: go further. To AASP & repair appointment.

• IF the question mark persists, follow these steps:

1. Press and hold the power button on your Mac for up to 10 seconds, until your Mac turns off.
2. Turn on your Mac and immediately press and hold Command (⌘) and R to start up from macOS Recovery.
3. While in macOS Recovery, use Disk Utility to repair your startup disk.
4. If Disk Utility found no errors or repaired all errors, reinstall macOS.
5. If you still need help, please contact Apple Support.

(..After due diligence: a conclusion either to fix, or replace unit; if unsuccessful.)

• Genius Bar Reservation and Apple Support Options - Apple

https://www.apple.com/retail/geniusbar/

[ Get hardware help ]

Good luck & happy trails!🍄