User level: Level 1 (25 points)Does anyone know what this is all about, on Golden Gate 27.2? I'm getting the same message on my iMac and my MacBook Air, which suggests it might be something to do with the newest version of macOS rather than a fault in my backup disks. Is anyone else getting this error? Is there a solution?
[Edited by Moderator]
Posted on Oct 31, 2026 8:30 AM
User level: Level 9 (72,871 points)Oct 31, 2026 11:49 AM in response to Ian_Osborne
Other users have reported this with the macOS 27 Golden Gate release, and your backup disks are likely perfectly healthy.
Some users upgrading to macOS 27 Golden Gate have encountered a file system issue where encrypted APFS external drives and Time Machine backup disks fail to accept correct passwords, repeatedly throwing the "disk cannot be unlocked" or "failed to mount" error messages. Because macOS 27 handles secure volume mounting differently, it triggers authentication logic failures across multiple machines—explaining why it's happening on both your iMac and MacBook Air simultaneously.
How to Resolve the Error
Do not erase or format your backup drive. Instead, follow these steps to bypass the bug and safely force the system to mount the disk:
Allow the Hidden File System Check (fsck) to Finish
When an encrypted backup drive is attached after a major system update, macOS often locks the volume to run a background disk check (fsck).
More info from Apple: Activity Monitor User Guide for Mac - Apple Support
Run First Aid via macOS Recovery
If fsck is not active but the drive remains locked, repairing the volume container from the boot environment usually resets the mount state:
User level: Level 10 (199,348 points)Oct 31, 2026 8:45 AM in response to Ian_Osborne
Are the Time Machine files stored on a Time Capsule? If yes, you will need to use an older Mac.......running an operating system of Sequoia or earlier to be able to access the data on the Time Capsule.
User level: Level 10 (148,617 points)Oct 31, 2026 11:05 AM in response to Ian_Osborne
google images says :
The image shows a standard warning triangle symbol overlaid with a circular camera or lens icon, typically used to indicate a camera error, connection failure, or hardware problem with a security camera, dashcam, or webcam app.
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You can not store anything but Time Machine files on a designated Time Machine Backup drive.
Those drives ARE locked for all other purposes, so that message appears to be correct.
What operation were you trying to perform when this message appeared?
User level: Level 1 (25 points)Oct 31, 2026 9:32 AM in response to Bob Timmons
No, my iMac's Time Machine drive is in a JBOD enclosure and for my MacBook Air, I use a USB drive.
User level: Level 1 (25 points)Oct 31, 2026 1:42 PM in response to neuroanatomist
That's great, many thanks. I'll give this a try. :-)
Originally posted at discussions.apple.com/thread/256386499