Fail to update macOS(Catalina, Big Sur beta): Unable to verify software update on a T2 chip Mac

Previously, I tried to install every Catalina update via Recovery Mode because it always failed in System Preference -> Software update.

Unable to verify software update

Reference: Reinstall from macOS Recovery , it said

That works well until I tried to install/upgrade Big Sur beta.

And because it failed to directly install Big Sur beta in Catalina on my machine, I tired to make a bootable usb drive from Big Sur installer. Then restart with holding Option key to boot into the installer. However it showed alert “A software update is required to use this startup disk”.

Then I hit Update, it ended up with the failure “An error occurred installing the update”. I guess my workaround doesn’t work anymore.

After researching for a while, I realized it’s a T2 chip Mac issue.

Then I changed my direction to research on T2 chip firmware, which is the approach to use mac configurator to revive/restore the firmware.

The article said:

And definitely make sure you backed up your mac and finger crosses!

The Revive Device doesn’t resolve the “unable to verify macOS” problem. Then I went Restore, it completely erased the disk. So I have to ‘Activate the Mac’ and install a fresh new Catalina.

Note: If you would like to install macOS on an external drive. You have to boot into Recovery mode and re-configure from Startup Security Utility, to set ‘Allow booting from external media’.

After the installation completed, go download and install the macOSPublicBetaAccessUtility.dmg, then download and install the Big Sur beta via System Preference -> Software update.

This time it passed the “Unable to verify macOS” error and successfully installed Big Sur! Then I use Migrate Assistant to bring back my backed up macOS data.

Update 12/16/2020

Later, I tried another way to manage to upgrade Big Sur beta.

  1. Restart your mac and hold on ⌘-R to enter recovery mode
  2. In Menu, Use Terminal and type: csrutil disable
  3. Quit Terminal and go ‘Reinstall macOS Big Sur’

This will reinstall macOS Big Sur and up to the latest beta.

Lastly, Good Luck!

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