When you install macOS Big Sur on these Mac models, the installer might say that the update cannot be installed on this computer, or your Mac might start up to a blank screen or circle with a line through it .
If your Mac no longer starts up successfully, these steps might help resolve the issue:
- Press and hold the power button on your Mac for at least 10 seconds, then release. If your Mac is on, it turns off.
- Unplug all external devices from your Mac, including any displays and USB accessories, and remove any card inserted in the SDXC card slot. Then turn your Mac on.
- If the issue persists, reset the SMC as described for notebook computers with a nonremovable battery.
- If the issue persists, reset NVRAM or PRAM.
- If none of these solutions work, please contact Apple Support for further assistance.
This article will be updated as more information becomes available.