Unable to access External Drives and Disk Utility after updating to macOS Sonoma.

Same issue here on Mac Studio running Sonoma 14.5. I tried 3 different SSDs (Samsung, WD, Kingston) and 3 different external enclosures (both usb-c and usb-a). Doesn't matter if it's an Apple Journaled disk, FAT, NTFS or anything. I tried them all...They worked for a day or two then gone. Disk Utility and System Report don't even recognise there's a drive attached. The drives and enclosures all work perfectly fine on separate Windows and Linux machines so this is clearly an issue from the OS.

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THIS WORKED FOR ME!

Here is what I did to get my 4TB LaCie mechanical drive to be recognized by Sonoma 14.2.1. I call out my mechanical drive because I also had an SSD drive not mount, but I think it just bit the dust.

When I got my mechanical drive, I formatted it Mac OS Extended (Journaled). To my understanding, this is fine formatting for a drive that will be used solely on a Mac and is compatible with most versions of Mac OS.

For this explanation, I will speak to what I did for the mechanical 4TB drive because my SSD drive never mounted on anything—it's a goner.

I started by finding a machine running a much older version of Mac OS. I happened to have an old laptop running Mojave. After it took ten years to boot up, I hooked up the drive and it mounted, but it wouldn't index the drive. I could see root folders but nothing inside. I opened Disk Utility and saw data on the drive because it showed how much space was occupied on the drive (in my case, 612 GB). I didn't attempt to repair the drive.

I then closed Disk Utility, right-clicked the drive icon, selected Get Info, went to the bottom of the window, and toggled the Sharing & Permissions carrot. From there I clicked the lock icon and unlocked the sharing and permission preferences. I then check the box next to Ignore ownership on this volume. I then clicked the lock and locked the setting.

After that, I restarted the laptop. Once it fully rebooted, I went in to double check that the box was still checked next to Ignore ownership on this volume. I had to perform this step (check the box and restart the laptop) a couple of times, but it finally took and remained checked. Once the setting was retained, I shut down the laptop running Mojave and moved over to my machine running Sonoma.

On the laptop running Sonoma, I made sure to remove items launching at login. I didn' want anything impeading the mount of my hard drive at startup. I then hooked up my drive and it mounted.

I hope this helps information is helpful for you.

A FEW NOTES:

I came to this realization becasue ALL of my current and old Time Machine drives ignore ownership and they had no issue mounting on my Sonoma laptop. So, I figured if form follows funtion, I replcated the same settings on the drive not mounting and it worked.

I am seeing a lot of callouts regarding ExFat drives, APFS and other sorts of drive formats...I can't speak to those specifics, but I would attempt to perform the simple (althought it took me hours of trial and error to figure out) process above and hopefully you'll be up and running in no time.

Cheers!

I now don't know what to do... I have had two USB-C Crucial 2TB SSDs corrupted by Sonoma 14.1.1 - possibly recoverable but I have lost all confidence in using them on my MacBook Air - these were being used to try to recover a SanDisk 128GB MicroSD card from a Nextbase Dashcam - I wasted hours trying to figure out what had happened to that - I now suspect it was Sonoma that corrupted it too. I've had cases where this and the Crucial's would show as unmounted but then find First Aid/fsck would be needed on next mount... 

we need to know when it is safe to use exFAT on Sonoma else at least for me I am going to have to switch to a W11 laptop for anything I need to do with exFAT... something I never thought I'd say that W11 would be a better and more reliable option... please be upfront and explain what is happening and when it will be fixed - I see many others with the same issue. Thanks

I saw in the release notes for 14 this:

• The implementations of the exfat and msdos file systems on macOS have changed; these file systems are now provided by services running in user-space instead of by kernel extensions. If the application has explicit checks or support for either the exfat or msdos file systems, validate the applications with those file systems and report any issues. (110421802)

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This did not work for me. My external drive is not visible at all in macOS. I can only see that the USB plugged in System Reports under the USB tab.

To be honest, I don't think Apple are interested..........They have to be aware of the issue and are choosing to do nothing. time to swap back to Windows

I run a Sabrent 4 bay external that does indeed act up on occasion, like individual drives dropping off.

Sadly, as the Mini i have only has 2 USB ports i use an Powered extender Hub (that works flawlessly with Monterey on the older Mini) that also had to host my Scarlett 18i20 audio interface (which also ran flawlessly on Monterey).

HAd top move the Interface to its own USB port as it seems the OS cannot handle it when it is on the Hub..

It will show that it still has Sync-Lock yet it will not pass audio - unless its in the Unique USB.

I see so many complaints about the ability of Sonoma to simply do its job..

Many regrets for "updating" - have wasted Hours with the new "features" as so many of us have.

Wish Apple could truly Upgrade rather than sending a new OS out to the real users - who find the problems their highly paid Engineers dont.

I dont like being a Guinea Pig, I want a product i can believe in again.

M1 MBA 2TB NVME SSD is not supported by macOS Sonoma, its mount once and when eject again its impossible to detect by OS, if its connected with some other OS like android in mobile then again connecting with Sonoma.

If I tried to copy large file its stoped and crashed and stoped working after around 25GB but this drive worked before without any issues in Ventura, after several updates in Sonoma upto 14.3 wont fix the issue, So I installed Ventura again drive working perfectly fine, I'm back to Ventura but when compare to Sonoma I felt my MBA M1 works speed and I think Sonoma limit the speed of M1

Last update NOT SOLVE the problem .

Only slow down the Mac.

the update brick the system during startup.

after 3 reboot the Mac works . But is slower than before.…. and sure I had to wait one hour to see the hard disk

my advice is stay miles away from this OS.

Expecially if you work with your Mac

I had the same problem.

I have seen prompt that just blink. I made screenshot and it's say "Allow accessory to connect?" and it was disappeared very quickly.

After Googling, I found solution for me.

Going to Settings->Privacy & Security->Scroll Down->Allow accessories to connect->Set to Automatically When Unlocked.

So, I connected SSD and it works well. After that I switch settings to "Ask for New Accessories" as was before.

I think it's bug in MacOS because disk or MacOS doesn't waiting answer from the user

I hope it helps for somebody

I'm not techy so apologies if not relayed properly but this has been my experience. I had a 5TB Lacie drive, after the upgrade to Sonoma, the drive will not mount. Spent 7 hours on the phone with an Apple "engineer". Changed security settings, modified different items on the computer trying to problem solve. Nothing. Then tried my old computers - no longer recognizable. The engineer could not figure it out. Told me I need to reformat my drive to work with Sonoma and try data recovery for my hard drive, probably will come with a cost. I gave up. Bought a new 8TB LaCie drive off the Apple site. (By the way I have the new M3 MacBook Pro. I waited to get the M3 because my iMac and MacBook are both no longer supported even though they worked perfect, they are circa 2013.)

New LaCie 8TB drive works for about two weeks. Then stops being recognized - after of course I had moved all my data to the drive. Spent another full day on the phone with Apple Engineers. No solution. They are escalating to Senior Engineers and will "get back to me". Expect 1-2 weeks. I sent them this thread.

Then I called LaCie. They have agreed to a "complementary" recovery on the 8TB drive I bought less than three weeks ago, but my other drive which is no longer under warranty, the original 5TB Lacie Rugged - they basically told me too bad. The 8TB recovery - likely will take 30 days.

I also have two WD externals and they seem to currently be working fine, but my LaCie d2 Professional (8TB) was also working fine for several weeks before it stopped being recognized.

FYI...M3 you cannot go backwards with the OS. No longer an option. If you can avoid updating to Sonoma - I'd recommend putting it off.

I was told by Seagate / LaCie this also happened with Ventura. Regardless - I'd be VERY careful with any external drives with significant data on a computer running Sonoma until they is resolved. Currently - NOT RESOLVED by Apple or Seagate / LaCie. As of right now, I would NOT connect it to your computer with Sonoma until this is fixed.

Here we are on March 12, 2024 and a new iteration of Sonoma was released last week, macOS Sonoma 14.4. The big question on this thread is. Does macOS Sonoma 14.4. fix the External Hard Drive connection issue that has plauged so many of us? My external drive problem has mostly been a great inconvenience and waste of time caused by initially upgrading an almost new 2023 Mac Mini M2 from Ventura 13.6.3 to Sonoma 14.2.1. After much frustration trying to get my APFS formatted 2T NVMe external drive to work correctly with Sonoma, I was able to restore my Mac to Ventura 13.6.3. Just like magic, my little 2T drive functioned perfectly again, just as it always had prior to Sonoma. I tried Sonoma again with versions 14.3 and 14.3.3 getting the same old same old with my external H.D.

I am reluctant to clean install Sonoma 14.4. only to again clean install Ventura 13.6.3 and restore settings and files via Time Machine back up to get my H.D. working again. I've become rather proficent and made a routine of upgrading and downgrading Mac OS software because of Sonoma. Why? I expect better than this from Apple.

HAd to power down yesterday... 

Didnt think anything of it as i have had to restart a BUNCH lately..and somehow was devoid of external HD issues...

or so i thought..

Upon the restart of the computer ALL of my external drives were GONE.

Took the USB HUB, mounted on my Monterey machine...NO DRIVES MOUNTING..

Remembered a post about going to Windows , did that and the drives are now back on Sonoma 14.4.

What the heck is going on ?? Unreliable OS that chooses to either see or ignore drives.... 

Come On Apple....

Do not throw your external hard drives out, your information is probably still there. I plugged in my 11yr old mac and my external hard drive still works there, but won't work on my new mac, it's definitely the Sonoma OS. Total Tech told me that Apple is working on a fix, but there was none as of last week.

Well, I also have this problem. There is no solution yet. I share my experience.

Previously: Kingston 2000 2 TB SSD worked on macOS for a year without any problems (and on ventura, and even on sonoma 14.1 for a while), and I also have a 2 TB Trascend HDD. My device - Macbook Pro 16 2021 1 TB. All these external disks were formatted after purchase in the format exFAT (to be available on both Mac and Windows).

A week ago, my SSD Kingston just started falling off, and my MacBook stopped recognizing it. I tried connecting it every now and then, either through a different cable from the HDD drive or through an adapter, but it was unstable—that is, it worked once and then it didn't work again.

1) At first, I thought the problem was with the storage device itself, but on Android, it connected quickly, and the files were transferred perfectly, without any delays. I mean, it works on Android.

2) Windows - I connected a ssd, it is recognized, but gives an error - and windows cannot fix it (as others wrote here that they managed to fix it this way - it didn't work for me) - that is, when connected, I had to choose "continue without checking for errors" and the folders open, but you can't copy them to Windows - it gives an error that the files are damaged. In this case, any file, even a video, even a small text document.

Therefore, it was not possible to extract the data using Windows. It doesn't work correctly (I think it's because of the disk format and MacOS was providing emergency assistance to the disk, so there are no permissions). I remind you that everything worked on the android.

3) MACOS - I have updated to sonoma 14.4.1 - and it doesn't work. The SSD blinks but is not recognized. And now my HDD disk takes a long time to connect - from 5-7 minutes until the Macbook recognizes it (before it was a minute, always!).

I restarted the system from safe boot mode via text support, and it also doesn't see the disk, but after restarting in normal mode, it recognized the disk once. In this way, I managed to copy the files to my disk. But the Finder started to freeze. And yes, after restarting, nothing works again. I repeated the event through this boot, then a normal reboot - and again the ssd started for one time. After disconnecting and reconnecting, it is no longer recognized. Emergency assistance is not provided - it also freezes, and the disk utility sometimes loads, sometimes not. In general, it doesn't work!

4) I tried to connect this SSD to my friend's MacBook, which has an old version of MACOS (9th or something), and it doesn't recognize it either.

....

So I don't know what kind of trouble it is, but looking at the stories of others, I'm sad that after spending a lot of money on equipment and disks, I can't work and it's not fixed by updating the system... Moreover, it happened suddenly and not even after the update, but until then it had been working for a year without complaints.

this has been incredibly frustating to me too! I have a samsung T7 SSD and noticed that my mac would not reliably read it after upgrading to sonoma software. I couldn't think of any other changes, but did not suspect that a software upgrade would have caused this problem. After reading several forums, I am shocked that this is a common issue from a macOS software UPGRADE. it's embarassing that apple pushed an upgrade that created problems rather than solving them.

Nowadays, I just plug in my ssd and wait 30-40 minutes for it to randomly show up on my homescreen...

the same drive is immediately recognized by windows systems.