In very rare circumstances, such as when a power failure interrupts macOS installation, your Mac might start up to a circled exclamation point. That means the firmware stored in your computer's memory needs to be revived or restored. You will need these items:
- Another Mac with macOS Catalina 10.15.6 or later, internet access, and the latest version of Apple Configurator
- A compatible USB cable to connect the two computers
For complete details, see Revive or restore a Mac with Apple silicon.
If you don't have the items you need, or you need help following the instructions, please contact Apple Support.