Mac OS Sequoia not recognizing USB Flash Drives

MJ wrote:

dwiser12u wrote:

I had to go through Apple Support. They say they don't have any history of this issue with updating to Sequoia.

That's bogus. Either Apple is lying or they maintain very crummy records.

Or very few people actually made official requests for support and asked for their support request to be escalated if the first line techs are unable to fix the problem. I think you over estimate how many people actually do this. I think many people just post on the forums thinking that will get Apple's attention.....it won't since Apple is not here on these forums.

Same here. I have a 4TB M2 drive mounted in an Acasis enclosure and then through a Kensington SD5700T Hub.

This worked perfectly fine without fail until update to Sequoia.

All hub ports and other connected hardware show in USB hardware report. The 4TB drive does not mount.

If I unplug the drive to hub or even the hub to Mac connection it appears as soon as they are connected.

Has anyone rolled back to Sonoma and its fixed the issue?

[Edited by Moderator]

Biggest mistake I made was updating to Sequoia. None of my USB drives are recognized. I've tried everything to fix this, but to no avail.

HI all - I found a solution that works for me but it's not ideal and does not solve the mystery.  I am on an M1 Mac airbook so it doesn't just happen with M2s.  I took all of the external thumb drives that were causing me a problem as soon as I updated to Sequoia… and I brought them to a second computer and took off everything that was on them...  That other computer was another M1 Mac airbook with an earlier operating system.  I reformatted the thumb drives and amazingly still no joy…. They would not mount on my desktop even though they show up perfectly under disk utility.. But grayed out so that they cannot be mounted.  I then took those same blank thumb drives and using disk utility I reformatted them as fat32 (did not try other formats because this is the formatting I wanted).  They then all mounted instantly as soon as they were formatted and now I have no trouble with any of them.  This is the same formatting I tried on a different computer but it just won't recognize them unless they are reformatted on the computer with the issue.   But all other computers can see then no issue. Not sure what anyone can do if they don't have a second computer to make their unreadable external drive content safe. I am set for now but mystery not solved.

Similar issue. Mac Studio M1 will not mount an XQD card (Formatted in Nikon Camera) and USB flash drives. SD cards in the Mac Studio slot work just fine. All worked smoothly before updating to Sequoia.

All cards and USB's show in Apple System Report with all details. Tried all the reboot etc tricks.

I have been in touch with Apple. Escalated case to OS engineers. Hopefully there will be a solution shortly. Very inconvenient.

I am having the same issues. New 2024 MacBook Air, M3 chip. SanDisk USB C Flash drive. It started to back up the first time I connected and failed to complete the back up. Now, I cannot get it to mount through disk utilities. Can see it greyed out. I can see it under the USB connections in system information. But, I'm stuck. Running Sequoia 15.1 Is there a fix for this?

Correct! I'd probably burn down the house trying to use Terminal.

Confirmed: 15.01 still not connecting external drives/SD cards.

Sequoia 15.1 update does not fix the problem, I still can't use my external storage. I feel very sad. (MacBook Air M2)

unfortunately 15.1.1 update didn't fixed USB drive failures

In my case the flash drive shows up in disk utility as Disk4.

In the Disk Utility you can mount it with the typed mount command, dismount or unmount is using the command and eject it using a typed command. It has a FDisk_partition_scheme of Windows_FAT_32

In Finder - Settings - General I have attempted the "Show these items on Desktop" and "Show these items on Sidebar" and the drive does not show.

Same for me - none of the settings mentioned in the above posts results in FAT32 USB flash drives appearing on the desktop or finder.

This is more than an inconvenience for me - I have a 3D printer farm that only works with FAT32 USB Flash Drives.

In many cases this is a USB C accessory issue.

Solution:

Use a basic USB 2 to USB C adapter

**NOTE: I was experiencing this issue. I was connecting my drives via an Apple USB-C Digital AV Multiport Adapter. This adapter was 100% the issue. Not the software. Not drivers. The adapter. Switching to a basic dongle/adapter resolved the issue.

My mother's 2019 5K iMac is the odd duck out that just won't do it. You can see the disks grayed out in Disk Utility but they will not mount.

The fact that these drives work on other macs suggest that there may be something installed on this mac that is causing a problem - perhaps some third party disk driver, or an antivirus or cleaner.

Please run Etrecheck and post its full report here. Use the "additional text" button and paste the report into the text box.

trying to get used to a new MacBook.. Sequoia, same problem.

however.. click on - about this mac:: system report:: hardware/USB - and there it is... click on it and it appeared in finder?

As recommended, restarted the MacBook, pop up asking if I trust the usb drive- all seems ok? Just about to try another one...