Mac OS Sequoia not recognizing USB Flash Drives

I am also having the same issue. I am using a Cruzer Fit drive, plugged into a USB-C adapter formatted to MS-DOS FAT32. Prior to this upgrade it worked fine, I have many files on this drive and could access, update and save with no issues. After the upgrade the drive does not show under locations in Finder; however, when I go to system information -> hardware -> USB it shows there under USB 3.1 Bus. Also, when I select a recent word document saved on this drive it gives an error that the file can't be opened. Frustrating as I plug the drive into another MAC and the drive shows in Finder and I sent some of the files through email. tried many reboots but the issue still remains, hopefully fixed soon.

I'm having the same problem and my LogiTech webcam won't connect via the USB port. Both USB drives and the web cam try to connect but will not stay mounted. With the USB drives I get repeated "Disk Not Ejected Properly" error messages because the drive connects for a second and then disconnects. The web cam seems to to the same thing. I've tried different USB ports on my Mac Mini and the result is the same. Updated to Sequoia 15.0.1 with no change. When I use iPhone mirroring I can use the iPhone as a web cam via the bluetooth connection. But the USB ports are the problem in Sequoia.

USB C adapters got my web camera working, too. All USB devices are plugged in to a USB dock that is connected via a USB C adapter. Working fine, now. Apparently the bug is in the regular USB port drivers.

I considered rollback to Sonoma using Time Machine. But when I called up Time Machine the only backups visible were ones made AFTER the installation of Sequoia. Have no clue how to sort that out, but Sequoia is not ready for prime time.

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

Brian Williams2 wrote:

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?

I believe that option is only available on the M-series laptops. The M-series desktop systems I don't believe have that option, nor do any of the Intel Macs (laptops or desktops).

Hey all, so I have a very strange issue. Similar to the other posts. I have a Samsung T7 ssd it is not recognised at all with my Macbook M3 Sequoia 15.0.1. When I plug an older SanDisk extreme it is recognised.

When I plug in the T7 with a USB c - USB c charging cable the drive is recognised. But obviously the data is very slow so not usable. I have tried the same hard drive with my ipad on ios 18 and not recognised. Plugging in the same hard drive in my mates ipad ios 17 it works.

I have been on the phone with apple support to bring this issue to them mentioned this forum. So hopefully something comes out of my hour on the phone.

DavidWMB wrote:

I reported the matter to MacOS Feedback, but Apple hasn't bothered to respond.

You did well to report it. There is never a reply unless they need further information. That's normal procedure, all feedback is read but usually they do not reply. The more people join their voices with respect to a given issue, the more likely it is to be fixed sooner.

dwiser12u wrote:

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

Probably because people are not contacting Apple directly for support. Apple won't know about any problems unless people make official support cases with them.

After trying many things, the support person had me upload the files from my Flash drive to my old computer, then using my MacBook Pro to erase my flash drives (that were already in FAT-32) and reformat my Flash drive with ExFAT. And finally, reload my flash drives with the files from my old computer.

It seems like a lot to have to go through for a system update.

If a drive is partitioned & formatted using another system, it is possible the other system configured the drive or file system in such a way that macOS does not understand. Other operating systems typically have more options for file systems than macOS does. Plus Apple rewrote the FAT/exFAT drive in macOS Sonoma which introduced some compatibility issues...any time a file system driver (or any driver for that matter) is created, it takes a long time to find all the bugs in it.

I make it a rule to always partition & format drives before using them in order to get rid of the factory image which could contain something that could cause problems. This way I know the partition & file system are compatible with my computer.

Plus, I had a USB stick which appeared to work fine when used with just a single computer. When I tried to use that USB stick on another nearly identical computer (only differed by a different version of macOS) I could not read the USB stick. Same thing happened in reverse if I erased the USB stick on the 2nd computer....the first computer could not read it. Found out the USB stick had a hardware issue.

On my Mac Studio M1 with 15.0.1 external flash drives (SD, CF) are not recognized. Diskutil does not show them with USB readers (I've tried 3 different). But the SD card slot on the Studio recognised a card.

On my MacBook Pro M2 with 15.0.1 everything works fine.

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.

I chatted with Apple Support for about 40 minutes on or around September 25, 2024. No solution, but the tech had me try a bunch of stuff, including re-booting into Safe Mode.

I also reported this on Apple Feedback (link posted somewhere in this thread) on or around October 1.

Attempting to connect my My Book external hardware. it shows on the system, however unable to access.

Any help is appreciated!

Closely related issue ... when re-booting, my external drive will not auto-mount.

2019 iMac 27-inch; Sequoia 15.0

Any thread dedicated to this issue?

They appear greyed out and will not mount although Time Machine is recognised.

Even using Apple connector does not work.

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

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