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

Hello, spent 20 hours to find the solution, with AI and other knowledge sources and .....

You won't believe: I use Eset Endpoint Security - after system upgrade there is an option to block all usb connected devices. Just tuned it off and all my external disks working properly.

It makes me crazy so I asked Chat GPT why it doesn't know that? Answer : you right, most of antivirus software after upgrade has that option and defaults settings are to block USB devices.

I hope it will help you guys :)

Thanks ! It’s been worrying me loads, because I’d just installed Tahoe on my iMac after a service and a wipe for a clean install, first thing i did was install my Eset Cyber Security id used for years, never thought about it blocking the USB, USB-C & SD Card slot, no warning, nothing, so i went here from Eset - https://help.eset.com/ecs_mac/9/en-US/computer_protection.html slid device control to off, then clicked Mount on each drive in Disk Utility and they appeared straight away ! I should have suspected Eset when it first happened, thank you 🙏

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]

davidjames1701 wrote:

I'm really feeling this is Apples problem with Tahoe ?

I have no problems mounting external drives with Tahoe, I routinely use 7 SSDs (and an NAS). See if the problem is present when you boot in safe mode, which disables 3rd party extensions and performs some system cleanup.

Start up your Mac in safe mode - Apple Support

This user (earlier in this thread) reported that drives mount in Safe Mode:

tpawluk wrote:

The drive works in safe mode. It mounts correctly. I have also tried First Aid and Erase in Safe mode. Both successful. But as soon as I start normal mode, the problem persists. :(

That puts the problem squarely on 3rd party software. Other users have traced the issue to 3rd party encryption utilities like the ones that often come preinstalled on new external drives (Samsung and LaCie/Seagate do this, for example), those apps may not be compatible with Tahoe. Personally, when I get a new external drive the first thing I do is erase it with Disk Utility, then set it up as desired (GUID/APFS, and with encryption if I want it on that drive).

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.

Thanks for putting me in the right direction. Did notice the extra connected devices option in ESET when it first appeared, but did not link it directly to my USB drives. They did connect but not mount, without any warning from ESET.

Thanks, that turns out to be a problem with my MacBook Pro 2019 - I lost 1 day trying to figure out what was wrong, and yes - it was Eset.

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

Barney-15E wrote:

NateKyngPresents wrote:

This is an Apple Forum, is it not? What a nonsensically rude response.

It is hosted by Apple, but nobody that actually works for Apple in a capacity that can affect macOS in any way monitors this Forum. If you want Apple to know about your dreams and desires, you need to actually contact Apple via their Feedback site, Feedback app, or call them via the Support website.

FYI, this thread is lost. I count at least six different external drive related issues here.

1. Issue with third party software.....the OP @tpawluck
2. Seagate proprietary software issue....@Psych13
3. File system corruption.....@syops
4. Hardware or compatibility issue with a dock.....@jaylynn0528
5. System Settings issue....@JameOgilviePhoto
6. Unknown--not enough details.....@davidjames1701 & @workshopbear

Each "Me too" user should start their own thread to get the attention their problem deserves. There is no way to help each person when their exact issue has a completely different source.

People also need to be aware that not every problem with their computer setup is due to Apple breaking things....four of these six issues are not Apple's fault (#'s 1-4, 5 is debatable). Upgrading to a new major version of an OS will always cause some third party app or devices to break...it is inevitable and it is up to those third parties to make their product work with the new OS usually by providing a software update for their third party software. Also, if a user has any existing issues with their computer, then a major OS upgrade will still have those issues plus possibly some new ones due to compatibility issues (again with third party apps & hardware).

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

are you running any security software ?

It’s very annoying. Try using a usb interface between your device and the Mac. It worked for me.

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.