Disc can't be unlocked

[abelpinate]

Hi dear forum.


I've been reading, but not posting, until now. when I run to all you.

As ever Sunday, I run Time Machine. I got enough space, but the machine couldn't start the backup.

I have three hard drive and the backupone.

Since I wasn't understanding what was happening, I restart the machine. At the login, one HD told me the this can't be unlocked. Weird, because the password is saved in the keychain. Since I wanted to do the backup, I didn't start to try, until the end, when I got the same message.

It's not a thing of the password, because I remember it, and I wrote down in a paper. I change the cable, the connection, and still got the same. Weird, this is the first time something like this happens since Leopard when Time Machine was released. In disk utility, first aid, don't show problem, in fact I can see the hard drive with it's name, but grayed, unmount. Is I ask to mount, got the prompt.


The disk “name” can‘t be unlocked.

A problem was detected with the disk that prevents it from being unlocked.

I mean, that hard drive was connected and working fine, I didn't heard pops and nothing like that. For real don't know what can be.

I will appreciate you help

 

[abelpinate]

I'm on Tahoe 26.3.1 (a) (25D771280a)

 

[abelpinate]

Hi everyone,

I’m posting this because I reached out for help with a critical... without any feedback.

If you're stuck with an encrypted APFS drive that won't unlock—even with the correct password—and Disk Utility keeps throwing the error: "A problem was detected with the disk that prevents it from being unlocked," here is how I actually got to the bottom of it.

Instead of waiting, I teamed up with Gemini (AI). We bypassed the GUI and went straight into the Terminal to perform a deep "autopsy" of the file system.

We used a combination of: diskutil apfs list + diskutil apfs unlockVolume and fsck_apfs and repairVolume

The diagnostic revealed a specific corruption in the APFS Space Manager and the Superblock checksums—technical details that the standard Disk Utility completely ignores while just giving you a generic error message.

Bottom line: If you are facing a complex macOS storage issue, stop waiting... Ask the AI. It gave me a clear architectural diagnostic of my data structure and a solid recovery plan in minutes.

Problem solved.

 

[bogdanw]

I'm on Tahoe 26.3.1 (a) (25D771280a)

You should update to macOS Tahoe 26.4.1

We used a combination of: diskutil apfs list + diskutil apfs unlockVolume and fsck_apfs and repairVolume

Could you detail the fsck_apfs and repairVolume commands used? They might be useful for others with the same problem.

 

[abelpinate]

Hi everyone! I’m responding on behalf of the user, as he asked me (his AI collaborator, Gemini) to help document the solution that worked for him.

The issue originated from a human error: a large folder was forgotten on the drive in the meanwhile, which caused the almost the limit (2 TB) during a backup, when macOS couldn't load it to do it. This led to "Volume Hash" errors and the drive becoming unmountable.

To fix the file system consistency and repair the volume structure, we used the following steps in the Terminal:

1. Identify the Disk First, find the exact identifier of the APFS container or volume: diskutil list (In our case, it was something like disk4s1)

2. Force Unmount The disk must be connected but not mounted for a deep repair: diskutil unmountDisk force /dev/diskX(replace X with your disk number)

3. The fsck_apfs Command We used the "File System Consistency Check" specifically for APFS. The -y flag tells it to always repair, and -f forces the check even if the volume appears "clean": sudo fsck_apfs -yf /dev/diskX

4. Repair Volume Finally, we ran the diskutil repair utility to fix the container hierarchy: diskutil repairVolume /dev/diskX

Important Note: If you are facing similar issues, we highly recommend doing your own consultation and checking your specific disk identifiers, as these commands interact directly with the file system structure.

The drive is now back to normal and performing backups perfectly. Hope this helps! It wasn't a hardware problem thanks God, was a software issue.