Mac Won't Boot or Start After macOS Big Sur/Catalina/Sierra Update

If your Mac won't boot or start after a macOS update, such as Big Sur, Catalina, Sierra, or an older version, there are 5 fixes you can try to get your computer up and running. Follow these steps to troubleshoot and resolve the issue. To make your Mac computer work again, you can try the fixes listed on this page.

Many Mac users have upgraded to macOS 11.0, but some have encountered issues with their Mac computers not booting after the update. While the upgrade is usually a smooth experience, some users have reported problems with their Macs failing to start up properly, making it essential to prioritize data recovery from the unbootable Mac.

• Your attempts to fix the Mac not booting issue may write new data on this Mac, which will overwrite the old data and make it irrecoverable.
• Recovering data before the complex fixes can avoid data loss.

Qiling Mac data recovery software can recover data from unbootable Macs, including creating a bootable media to recover data from a Mac's hard drive, recovering data from a failed internal Mac hard drive, APFS boot drive, and unmountable APFS boot volume. If only one Mac is available, it can be used to recover data, but if two Macs are available, the hard drive can be removed and connected to the second Mac to use Deep Data Recovery for Mac to recover data.

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To resolve the "Mac won't boot after update" issue, first, restart your Mac in Safe Mode. If it boots successfully, you can try troubleshooting the issue.

1. Reset the PRAM / NVRAM 

NVRAM stores data like volume settings and screen resolution, and resetting it won't harm your Mac, it may even restart normally.

• Restart your Mac
• To reset the NVRAM on a Mac, press and hold the "Command", "Option", "P", and "R" keys, then turn on the computer. This is the same combination of keys used to reset the PRAM.
• Once the Mac has restarted, release the keys and let it boot up normally. The keys should still be held down during the restart process.

If the progress bar fills up and the Mac starts up, you're probably good to go. If not, reset the System Management Controller (SMC).

2. Reset the SMC

In some situations, you may need to reset your Mac's SMC (System Management Controller).

• Shut the Mac down.
• Unplug all cables.
• Wait for a few minutes. 
• Plug the cables back in and start up the Mac.

Unplug your Mac desktop, wait 15 seconds, plug it back in, wait five seconds, and then press the power button.

3. Boot Mac in Safe Mode

Safe Mode is a stripped-down version of the Mac operating system that can be useful if you are trying to troubleshoot issues with your Mac.

• To start, turn on your Mac and hold the "Shift" key. Ensure that your Mac has at least 9 GB of free space available.
• Release the shift key, log in, and restart the device, potentially requiring a second login if FileVault is enabled.

Wait patiently till Mac computer finish the reboot process.

4. Run Disk Utility in Recovery Mode

If your Mac boots but the operating system won't load, it might be due to a corrupted drive. You can fix this in Recovery Mode, where you can restore from a Time Machine backup, use Disk Utility to repair connected drives, check your internet connection, get online help, or reinstall macOS.

• Make sure the Mac is turned off. If it's stuck on a grey, blue or white screen, hold down the Mac's power button for several seconds until it shuts off.
• Hold down the "Command" and "R" keys, and power the Mac back up again, keeping them pressed while it boots up.
• Once your Mac starts in Recovery Mode, click on "Utilities", then select "Disk Utility", locate the icon for your Mac's drive, and click "Verify Disk".

5. Reinstall macOS Big Sur/Catalina/Sierra

If macOS Big Sur, Catalina, or Sierra fails to boot after an update, there are a few methods to try and fix the issue, including running a System Report, checking for firmware updates, and resetting the System Management Controller. However, if none of these methods work, the last resort is to reinstall macOS.

• You can download macOS Big Sur/Catalina/Sierra and create a bootable USB drive to clean install them on your computer again.
• To boot into Recovery mode, you can restart your Mac and immediately hold down the Command (⌘) + R keys. This will open the macOS Utilities window, where you can select "Reinstall macOS" and follow the onscreen instructions to install the latest operating system. Alternatively, you can also reset your Mac to its factory settings by following the steps outlined in our article, which includes reinstalling macOS.

If your Mac doesn't respond after trying these troubleshooting tips, contact Apple Support or a certified Apple Repair Center, as the issue may be with the logic board or other internal hardware.

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