Tahoe not recognizing External Hard Drives that still work fine on Sequoia

Apple has a real problem. I can't offer a solution but this needs to be shared so Apple can see this is a real bug that must be addressed.

Two of my external drives will not mount after macOS 26 upgrade. Both external drives are Thunderbolt. One was raid 0 made up of four SATA 4TB SSDs and the other was a SAS U.2 NvME Micron9300 Pro 15TB SSD.

Picture included is of Disk First Aide unable to fix the external RAID 0 array with the same results for the U.2 drive. Attempts to mount in terminal even in read only mode had your same results in failure.

Apple has no solution with my open support case and has been elevated to the engineering group.

I was able to mount both external drives with MacDrive Pro 11 from OWC. I did migrate as much data as I could to the server. The both volumes appears to have file system corruption now.

[Edited by Moderator]

You could try this:

Potential Issues and Solutions 

• Drive Not Mounting: Some users have reported that Tahoe doesn't recognize external drives.
  • Check System Settings: Go to Apple menu > System Settings > Privacy & Security and ensure "Allow Accessories to Connect" is set to "Automatically when unlocked".
  • Reboot: Sometimes, a background process after a failed mount attempt can eventually allow the drive to mount; check the Terminal for a fsck process.

Restart in Safe Mode and test. If OK then restart normally and retest. I have several drives and no issue.

I'm having the same problem on my Macbook Air. Connected my Seagate external drive just now where I store my Photos library and got the message that a driver needs to be installed....it told me to disconnect my drive and restart my laptop-which I did....but I then just got the same prompts and was asked to do the same thing. Most frustrating. And yes, I, too, upgraded to Tahoe 26.0.1 just today.

See screenshots below. Interestingly, when I connect my Kingston Ironkey Vault Privacy 50 USB, I don't have any issues. It's my Seagate drive that has issues.

[Edited by Moderator]

Bugs can be reported to Apple here:

Feedback - macOS - Apple

Check System Settings:•  Go to Apple menu > System Settings > Privacy & Security and ensure "Allow Accessories to Connect" is set to "Automatically when unlocked".

The author already stated it is a Mac Studio, not a Mac laptop, so that setting will not exist.

I've checked my Allow Accessories, and I've also rebooted my Macbook Air, and still no luck, with Tahoe 26.0.1.

Thank you neuroanatomist: I reported this bug. The more reports they receive, the greater the chance they will come up with a fix.

I restarted it in safe mode and it still did not recognize my external drive. What is the next step in trouble-shooting? Apparently, it recognizes my external drive when it is directly connected to my laptop but not to my USB dock which is how I upload my images. I am quite perplexed now.

jaylynn0528 wrote:

I restarted it in safe mode and it still did not recognize my external drive. What is the next step in trouble-shooting? Apparently, it recognizes my external drive when it is directly connected to my laptop but not to my USB dock which is how I upload my images. I am quite perplexed now.

Is the Dock powered? If it is just using bus power, there likely isn't enough current to support the dock and even one drive connected to it.

How do I restart in safe mode? I am having the same problem and do not want to lose my images that are on the drive.

jaylynn0528 wrote:

How do I restart in safe mode? I am having the same problem and do not want to lose my images that are on the drive.

Start up your Mac in safe mode - Apple Support

If it's perhaps Fusion drive setup.... you are out of luck ;(

So, any update so far? I have the exact issue.