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

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 ?

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 🙏

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).

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]

ajlholt wrote:

I have a complex external drive set up with multiple data drives (some with partitions) for storing media. These all back up to a Synology Diskstation with Carbon Copy Cloner software via a Macbook Air. The drives are daisy-chained starting with a USBC to Thunderbolt 1 adapter. Everything was working fine till I 'upgraded' to Tahoe. Since then everything has been going wrong. Drives would either connect then disconnect without ejecting properly (bad news for backing up), or would not connect in the first place. It has not even made a difference connecting individual drives directly to the computer. This is not a problem with anything to do with third parties. The problem is with Tahoe. Everything worked fine before. I have gone to System Settings/Privacy/Accessories and changed tried both 'Always allow' and 'Automatically allow when unlocked' but neither have solved the problem. Apple, you need to sort this out.

I would suspect drive cables and adapters. Apple has been trying to improve performance & reliability, but it has the side affect of requiring shorter & higher quality cables. I've seen a number of users on this forum complain of drive related issues which disappear once replacing their current cables with higher quality cables.

FYI, if one drive closer to the computer drops out, then all the others will follow as well. Is your daisy chaining of devices exceeding the cable lengths & numbers for the protocols you are using with those drives & devices?

As for the Synology NAS, there have been reports (not just with Tahoe) about macOS networking connection issues the various types of network shares. While most of them have to do with Time Machine backups to a NAS, there are also many basic network share related issues as well. A search of this forum for the past year may provide you with some insights, unfortunately I don't recall specific details. You should definitely make sure your the software & firmware for you Synology's NAS is up to date. I also know that SMB configurations on the Synology are also critical for macOS compatibility.

Also, I would leave the "Allow accessories to connect" configured to "Always when unlocked" or whatever the equivalent is for the particular version of macOS (Apple unfortunately keeps changing the wording). Depending on circumstances and how you utilize this setup....the "Always Allow" may be appropriate if the "Always when unlocked" option is not sufficient. Unfortunately Apple's default setting usually causes too many problems.

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.

ajlholt wrote:

Thanks. Things are working now but there was definitely an issue with longer cables. I had also not realised that Thunderbolt is a much more capable connection than USBC.

Glad to hear that replacing the cables resolved that issue for you. Thanks for the update.

AbedinShanto wrote:

I’m having the same issue. Could you point me to the post that explains it or the guide on how to turn it off?

The best thing to do is completely uninstall any anti-virus software, cleaning/optimizer apps, and third party security software by following their developer's instructions. These types of apps are not needed on a Mac and usually causes more problems than they solve since they interfere with the normal operation of macOS at a very low level. macOS already has great built-in security especially when the user also practices safe computing habits as outlined in the following article:

Effective defenses against malware and other threats - Apple Community

Thanks. Things are working now but there was definitely an issue with longer cables. I had also not realised that Thunderbolt is a much more capable connection than USBC.

ajlholt wrote:

I have a complex external drive set up with multiple data drives (some with partitions) for storing media. These all back up to a Synology Diskstation with Carbon Copy Cloner software via a Macbook Air. The drives are daisy-chained starting with a USBC to Thunderbolt 1 adapter. Everything was working fine till I 'upgraded' to Tahoe. Since then everything has been going wrong. Drives would either connect then disconnect without ejecting properly (bad news for backing up), or would not connect in the first place. It has not even made a difference connecting individual drives directly to the computer. This is not a problem with anything to do with third parties. The problem is with Tahoe. Everything worked fine before. I have gone to System Settings/Privacy/Accessories and changed tried both 'Always allow' and 'Automatically allow when unlocked' but neither have solved the problem. Apple, you need to sort this out.

I have many drives connected to my M4 Mini including USB3 hub, Thunderbolt 2 arrays, and USB-C. I have no problems with any of them on Tahoe.

On rare occasions I connect a drive to my MacBook Pro (M2) without issue.

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]