Level 1

14 points

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

I have upgraded my Mac Studio to Tahoe 26.0.1. Since the update, it refuses to mount any of my external Hard Drives, even if they have been formatted in APFS. I have tried to format them again from the MacStudio, and there is an error: "unable to mount". They were working perfectly fine up until the update. I have a MacBook Pro that I have not upgraded yet (still working on Sequoia), and that one recognizes the external drives without problem. They mount perfectly, and I can add and delete files normally. I have tried different ports and cables for the MacStudio to connect to the Hard Drive, but no difference. And they all work on the other Mac.

Any ideas why? It seems to be related to Tahoe, since it happens to all 3 of my external drives, but they all work in the one I have not upgraded yet, and they were all working until the upgrade. I have tried manually mounting them. I have used the Terminal and it says "successfully mounted," but it is still grayed out in Disk Utility and shows as not mounted. I have tried restarting several times, and I have checked for system updates and installed them all. Any ideas? Thank you!

Mac Studio, macOS 26.0

Posted on Oct 1, 2025 10:46 AM

Top-ranking reply

Przemekfx

Level 1

32 points

Posted on Oct 20, 2025 2:37 AM

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 :)

View in context

38 replies

Oct 13, 2025 8:59 AM in response to tpawluk

Hi, glad I've found this, I've exactly the same problem on my iMac i7, worked fine before, but after I upgraded to Tahoe, no external drives are recognised, show up in disk utility ok, and I can re format them, but will not mount at all, when I click "Mount" nothing at all happens, but if I plug the same drive into my 2013 MacBook Pro, it recognises them instantly, I'm really feeling this is Apples problem with Tahoe ?

Barney-15E

Level 10

122,042 points

Oct 19, 2025 10:37 AM in response to NateKyngPresents

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.

Psych13

Level 1

32 points

Oct 10, 2025 9:45 AM in response to AlWeir

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

Psych13

Level 1

32 points

Oct 10, 2025 10:04 AM in response to neuroanatomist

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

Nov 2, 2025 1:09 AM in response to pawel_78

I tried using a usb interface and then it worked easily. Very strange issue. Just something to remember maybe, for next time.

Oct 5, 2025 10:56 AM in response to neuroanatomist

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.

Barney-15E

Level 10

122,042 points

Oct 5, 2025 5:33 PM in response to jaylynn0528

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.

Barney-15E

Level 10

122,042 points

Oct 12, 2025 5:02 PM in response to syops

syops wrote:

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.

Then you should probably tell Apple.

None of us work for Apple and we also can’t make the “bug” happen.

Oct 14, 2025 11:42 AM in response to tpawluk

I tried several drives. An older Seagate drive now works, which didn't before, and my Samsung T7, which contains all my sample instruments, doesn't. I am beyond annoyed. I do hope Apple fixes this soon, I have stuff I need to be getting on with. (safe mode had no effect at all).

tilleron

Level 1

8 points

Dec 4, 2025 3:20 PM in response to AlWeir

I do not even see that as an option on Mac OS 26.1

"Allow Accessories to Connect" is set to "Automatically when unlocked". Does not exist on either of my Macs running 26.1 where are you looking?

Pasting that into Mac Help says Content is Not Available.

Dec 4, 2025 3:44 PM in response to tilleron

tilleron wrote:

I do not even see that as an option on Mac OS 26.1

"Allow Accessories to Connect" is set to "Automatically when unlocked". Does not exist on either of my Macs running 26.1 where are you looking?

Pasting that into Mac Help says Content is Not Available.

What Macs? The setting is present only on laptops, not on desktops.

Dec 4, 2025 7:31 PM in response to tilleron

Ok, that means the option you're looking for is not there because it's not supposed to be there.

See the comment by HWTech:

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

Not sure which of these you fit into, but perhaps you may want to start your own thread as deconvoluting this 3-pager is perhaps not the most efficient use of time.

Oct 5, 2025 7:51 AM in response to tbirdvet

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.

Oct 5, 2025 8:09 AM in response to jaylynn0528

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

Hevisko

Level 1

5 points

Oct 6, 2025 3:46 AM in response to tpawluk

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

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