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

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Posted on Jan 1, 2026 10:01 AM

Update, I’d installed my security software before checking external hard drives, then I noticed I couldn’t access them, then I came across a post explaining it, my security software Eset, blocks access to installed external HDD’s by default, found how to switch that off and they’ve been fine since, I suspect that most similar software does this ?

63 replies

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.

Oct 20, 2025 2:37 AM in response to tpawluk

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 :)


Dec 14, 2025 8:56 AM in response to Psych13

I can relate to all these problems. My entire life is on several external HDs. I'm a writer, and everything I have to show for my hard work is on them (I never save to my MacBook Air that I bought last year or any before that bc of ruinous problems to my simple documents, etc.). Is it Tahoe, Vectotech's hard drives that I've been using of late? The fact that life is basically one problem after another lol I just had an Apple Genius Bar appt, and they fixed the problem I went in for, totally unrelated. And they explained and described everything they were doing. Great. Now this with the hard drives, and my hunch is Tahoe 26.1. I've never had problems with Vectotech external HDs. I don't even really know what my point is! Just commiserating with people who've had similar issues. I'm going to make a Genius Bar appointment again, because I'm no computer expert, and I am NOT downloading software that is a scam and makes things worse. I will update as this problem evolves (it's getting worse right now) and hopefully resolves. Good luck to all and talk soon.

Dec 27, 2025 9:45 AM in response to MaestroDDHughes

MaestroDDHughes wrote:

Maybe read the whole thread before mindlessly replying

FYI, the default Sort Order on this forum is "Ranked" which places the posts in a random order. Most people don't realize this which makes following the thread very difficult. Even the regular forum contributors get caught at times when we don't realize we've been logged out & the "Sort By" option reverts to the default "Ranked" random ordering.

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

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