Sequoia update has caused mounting issues with external hard drives. Ex: had one working and then all of a sudden M3 Max MacBook Pro stops recognizing the device. Now, it won't even find it when it's plugged in. Device works fine on other devices.
In my case, since I installed Sequoia, I can hardly ever eject any flash memory. It always tells me that I can't because they are in use by some other program. I have to force eject or shut down the laptop. With every upgrade I see Apple's quality and confidence drop a lot!
Wish this was a fix, but it's not. (Plus, the instructions for resetting the SMC controller on Intel-based desktops differ from what's posted.)
This bug, which seems to have been around at least since Sonoma, manifests differently across machines, is not confined to any one type of connection/cable and, unfortunately for the purposes of escalation, isn't a global issue.
It is, however, persistent and a major pain. (Note: after 15.3.1, my external drives are now all working, but two of the three—the USB-C drives—will not unmount.)
Yes, it was not the fix. I’ve only had issues with large (5TB) portable drives, Seagate and WD connected via a powered USB hub. Occasionally, the drive disappears especially after a reboot or startup if my Mac Mini M4 Pro has been shut down for some reason. After trialling the SMC and NVRAM fix, the external drive just didn’t show up as connected. My only way to get the drive to reconnect has been to plug the drive into my old 2014 Asus Windows Laptop running W10 and running the Check Disk tool. It always shows there are errors but fixes them and then when I replug back into my Mac Mini, it shows straight away.
What is a powered monitor or USB hub? I’m having the same problem with my sequoia update since the end of February 2025 I cannot use my external drives without them freezing or acting weird turning off and on.
Tinx_Lvs_JC wrote: "...Apple - please fix this bug!..."
Apple isn't here — use this form:
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carlamm wrote: "...APPLE DO SOMETHING!"
carlamm ~ Apple isn't here in these user-to-user communities. Instead:
Contact - Official Apple Support
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SimplyArt wrote: "Apple! You have been my "rock" (...) Apple, please give us..."
SimplyArt ~ Apple isn't here in these user-to-user communities. Use this form:
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GizinUK wrote: "...Apple sort this as data loss is a critical issue."
GizinUK ~ Although Apple administers these user-to-user communities, that doesn't include reading each of thousands of daily posts for possible feedback. However, you can tell Apple to "sort this" here:
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I have same problem with my MacBook Air M1. I recently upgraded to Sequoia and now I get Lacie Hard disk cannot be found.
Same problem, exFAT not working normally, super slow responses
Perfect. I nearly went and bought another drive. Switching it for a hub to the socket at the rear of the Mac sorted my problem. Thanks.
I am trying to find this - when I search for it - it points to privacy and integrity, but it is not there. Why did I do this. I have all my files externally
I just updated March 2025 and I have all sorts of problems
I had Raid Time Machine drives that worked fine with Ventura and Sonoma. Once I upgraded they would not mount and actually crashed the computer and forced a restart. Apple Store has been helping me with this issues with no luck. They’ve decided to reinstall Sonoma. Hopefully Apple figures out what’s wrong with Sequioa before I need to upgrade to it for other software reasons.
Hi it is depending of the puter you use!
The problem seem to be a re writing of Spotlight on the External Hard disk. That use a lot of space and block the process.
Apple , this afternoon, work on the problem !
So be patient !
A work around: Select Finder: GO: Computer:
You should see the mounted external drives which you can then use in the normal manner.
Its a Bug in OS 15.2 that doesn't allow this to show up in the finder side bar nor in the desktop even when these defaults are selected in the Finder Sidebar settings.
Sequoia 15.0 bugs - external hard drives
