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Mac OS Sequoia not recognizing USB Flash Drives

I just updated my iMac M1 to run Sequoia and now my USB flash drives are not recognized. My external hard drives are recognized as are my external SSD's. I have seen online that I am not the only one with this issue, but nowhere have I found a fix. Is this something that can be fixed or do I have to wait for a update?

iMac 24″, macOS 15.0

Posted on Sep 19, 2024 8:32 AM

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Posted on Sep 26, 2024 3:13 PM

This is driving me nuts. After initially updating to Sequoia yesterday on my M2 Macbook Pro, my USB Dongle device initially mounted fine, automatically. Today it won't mount automatically.

It's recognized, in that I can see the device in Disk Utility. However, the button to mount in Disk Utility does not work.

I can only seem to mount the device through Terminal by performing the following steps:

1) Call up the disk utility list

diskutil list

2) Find the DriveIdentifier for the USB device in the list

3) Create a Volume to mount the device:

sudo mkdir /Volumes/YourVolumeName

4)Mount the device to this volume

sudo mount -t msdos /dev/DriveIdentifier /Volumes/YourVolumeName.


It's a USB2.0 device plugged into an apple USB-C multiport adaptor, the drive is FAT32 formatted. Allow Accessories to connect is set to Always. Finder settings are on to show External Disks in Locations on the sidebar.


And the kicker: This same USB device mounts automatically w/o issue on my M1 Mac Studio updated to Sequoia the same day! What gives Apple? Please address this issue ASAP. We should not have to run terminal commands to mount USB drives. This is not a viable work around for users who do not have admin permissions. Thank you.

75 replies

Oct 14, 2024 10:06 PM in response to Lilisbuddy

Same issue here.


Disk has been in regular use with no issues until updgrade. Also works fine on second older imac also running sequoia


Disk shows in disk util but is greyed out and will not allow me to mount it



I tried mounting the disk using terminal but it gives me the following error:


mount: /Volumes/drive6s1: invalid file system.


Sys info for disk...





Re-formating as suggested in other threads does not work...




Sep 25, 2024 2:31 PM in response to MJ

MJ wrote:

In my case, no the drives really aren't mounted.

I CAN manually mount them using Disk Utility, but that is a pain.

Are they encrypted? I have seen older versions macOS not automatically mount encrypted drives....not even offering to provide a prompt to unlock them. I believe I have even seen the same for un-encrypted USB drives before, but I am not 100% certain. I never had the time to look deeper the issue since were Macs in my organization & the user was not complaining about it....I only noticed it while working on the devices.

Sep 27, 2024 11:21 AM in response to Lilisbuddy

I have had this issue, in particular when I try to dump a .stl file for my Prusa Printer, which ONLY reads a Fat32 formatted USB. I will put a small, empty Fat32 USB drive in my M2 MacStudio running Sequoia 15.0 and if I try to copy anything from a 1k text file to a 50Meg .gcode file my Mac pukes and says there is no room on the drive. I have tried reformatting using Disk Utility to no avail. But..... I have succeeded and now use Path Finder from Cocoatech and that works perfectly. I have always used Path Finder off/on and I like it for some specific things. Now it is invaluable so I can work interchangeably with Fat32 USB drives. BTW, I saw this too on my old MBP which was the last Intel MB Apple made running both Ventura and Sonoma and they did not like Fat32 drive too. I don't know of an Apple solution to this issue. While one may exist, I can say that Path Finder works every time.

Sep 27, 2024 12:04 PM in response to Lilisbuddy

Same issue Late 2023 Macbook Pro 16 M3 Pro 18GB

15.0 (24A335)


Just called Apple about it, and they want to take it in for service


Weird behavior from any type of mass storage.

Initially I tried moving some files from my NAS to a known working SD Card formatted w/FAT32.

It hung, so I had to cancel it. Then I noticed I couldn't format it, stuck "Creating partition map", it wouldn't auto mount


So I tried various flash drives, some worked okay, then broke just a few minutes later.


Some USB drives wouldn't show up at all in Disk Utility, even when booting directly into recovery mode.


On the support call we ruled out faulty flash drives, and USB C adapters.

Sep 28, 2024 5:55 AM in response to PVRP

PVRP wrote:

I have a similar issue with M1 Air and Sequoia (after updating), my external SSD in a HUB is not mounting.
The fix is to activate the option in security, always ask to connect accessories. Not ideal, because now a I have to allow everything I plug.

Once it asks about the one device, you can set that back to something else. It should remember the devices you approved.

Mac OS Sequoia not recognizing USB Flash Drives

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