Mac OS Sequoia not recognizing USB Flash Drives

Same problem..... Wish I hadn't updated → really a pain.

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.

The MacBook Air M3 did not recognize the USB after updating to OS Sequoia V15.0. Is there a solution to this problem?

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.

I have the same problem with SATA disks that are connected to the Mac via a USB to SATA adapter.

When I turn on the adapter after having connected the SATA disk, the disk powers up.

I then see what seems to be the confirmation dialogue that would ask me if I want to allow this device to connect.

However, this window disappears right away before I can even read its contents.

The disk is not available: it does not appear in Disk Utility and also is not listed in the output of the command line input "diskutil list“.

I have to go to the security settings in System Preferences and change the setting to always allow devices to connect.

Then, the disk appears.

Afterwards, I can switch the setting back to ask before allowing new devices to connect.

This seems to be a bug in macOS Sequoia.

Reported to Apple in FB15409558

Hi. You wrote "Allow accessories to connect,". I am on 15.0.1 and cannot find this option in Privacy & Security. Apple documents say it's there, but I don't see it. Where did you find it?

Regards, Brian

In my case, the non-recognizing of USB drives occurs irrespective of whether the drives are plugged directly in the USB ports on my MacBook Pro with Sequoia OS, or indirectly through a USB hub, like the CalDigit docking station or USB hub.

None of this ever happened with Sonoma OS!!

It is absolutely ridiculous that Apple has not fixed this as yet with an update. How am I to work like this?!

Hello people of the world,

I was able to connect external SD card to my M1 mac using a following workaround.

diskutil list

This allowed me to see IDENTIFIER of the drive

diskutil mountDisk /dev/diskX

Where X diskX is value found in terminal - IDENTIFIER

That mounted a drive and I was able to drag n drop.

Be well, I found this on reddit, user u/wowza42 mentions this 4! months ago.

I hope iCloud security team has a different management :D

Are they actually not recognized, not mounted, or not showing on the desktop? These are three different things, and it would help if that could be clarified.

1) Not recognized would imply that they do not show at all in Disk Utility. Is that what is happening?

2) On another level, they could be recognized, but not mount - they would appear in Disk Utility, but show up as "not mounted" - in which case you might try clicking on "Mount" and see if they become available.

3) The third possibility is that they do mount but simply do not show on your desktop - that is a mere Finder setting. Make sure that all the boxes are checked in Finder->Settings->General, under "Show these items on Desktop".

So, to be sure, are we talking of case 1, 2, or 3?

Sorted now. Erased HD and reinstalled Sequoia, migrated data and loaded apps manually from Adobe etc. Mounts all USB drives and XQD and SD cards in seconds. This method although tiresome, eliminates old bits of stuff that was conflicting with sequoia.

Anyone running into this issue, please open the System Information app by:

• Holding the Option Key
• Clicking the Apple logo on the top left
• Click "System Information"
  • If your issue is with USB devices and card readers, click USB and report if the USB device in question shows up.
  • If your issue is with the built in SD card reader, click Card reader.
• Screenshots of this page will be helpful.

Please also tell me the following:

• What device you are trying to plug in, model and brand
• How the drive is formatted (NFTS, exFAT, FAT, Mac OS, etc)
• How it's plugged in (via a simple USB-C adapter, or USB-C Hub)
  • The brand and model of the adapter or hub
• Have you done a clean install of Mac OS Sequoia, or an upgrade over Sonoma.

If you have issues, try a reboot and report if that fixes the problem.

• I have personally witnessed Disk Utility stop working, if a previous formatting operation failed. Only a reboot would make disk utility work again.

Try booting into recovery and see if the device shows in DiskUtility

• These Steps are for Apple Silicon (M1-M3)
  • Shut down your Mac
  • Hold power button until you see Startup Options
  • Enter your password
  • Open Disk Utility
  • Report if your device shows in recovery mode.

Usb drives still not working. Where are you now Steve Jobs when we need you?

Thank you, Luis,

SD cards appear in Disc Utility but are greyed out.

They will not mount.

They do not appear on the desktop or in Finder.

External Time Machine functions normally.

Fujifilm X-T5 camera connects normally when tethering

but will not connect to Fujifilm X-Raw studio.

Hopefully, Apple will get a move on with a revision.

So this is interesting. I found a discussion post from 2011 where someone said to reboot the computer with the usb drive connected and that... got it to mount on my 2019 5k iMac. in fact, I was able to eject and reinsert my FAT32 formatted thumb drive and it mounted successfully the second time too. I'm looking at it right now.

Fat32 formatted disk partitions do not mo… - Apple Community