Mac OS Sequoia not recognizing USB Flash Drives

Solved:

I (unfortunately) updated 2 Airs and a Pro to Sequoia and had trouble with them recognizing all external hard drives and flash drives after the update. Luckily I saw a security (hand icon) window flash quickly on one of them as I was plugging a drive in. So I thought it might be a security issue, scrolled down in Settings->Privacy and Security -> Accessories. Setting the option to "Always Allow" makes it work. Setting it to Always Ask does not seem to work since the window just quickly flashes by, not allowing you to confirm access. Enjoy!

code cowboy wrote:

So I thought it might be a security issue, scrolled down in Settings->Privacy and Security -> Accessories. Setting the option to "Always Allow" makes it work.

I would suggest setting it to "Always when unlocked". It will achieve the same goal as "Always", but is a bit more secure since devices cannot be connected when the laptop is locked when you are away from it.

Had a similar problem on Sequoia (15.3 I think?) on M1 Macbook: USB flash drive did not show up in Finder or in Disk Utility but DID show in system diagnostics. Here was the fix: when I connected the USB flash drive, for a fraction of a second there was a pop-up asking if I wanted to allow the device to connect. I had to make a slo-motion movie with my iPhone to read it. To resolve that, I had to go into settings and switch from asking me to allowing USB - I set it to Automatically when Unlocked. Worse for security, but after that the drive showed up immediately in Finder.

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

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.

I had the same problem with both of my M3's, Sequoia 15.2, external drives not working. Turns out, it was the USB-C to USB adapters that I purchased directly from Apple. They used to work, and now they don't. I had a generic one laying around that was much smaller (USB directly to USB-C without the cable) and it worked fine on both laptops!

So, for anyone using the official Apple adapter, try another one. Link for reference: USB-C to USB Adapter - Apple

The ones that did work are on Amazon, currently $8.99 for two, with the following name:

Syntech USB C to USB Adapter Pack of 2 USB C Male to USB 3.0 Female Adapter Compatible with MacBook Pro Air 2024, Microsoft Surface, iPad,Samsung Notebook, Dell XPS and More Type C Devices,Space Grey

I downloaded the Sequoia 15.0.1 update that was, I believe, was posted today which has resolved my inability to use FAT32 formatted USB flash drives.

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.

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?

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.

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.

I had the same issue with a USB Key (originally formatted from Win). On Sonoma it was working fine but it was not auto mounting on Sequoia. I did re-format it on OSX and now it is recognized and auto mounted.

Well, got my M4 Pro MBP yesterday and, as expected, my 2TB Kingston KC3000 SSD in the IcyBox enclosure was not detected (just like on my M1 Pro MBP with Sonoma). Started a chat with Apple support, went through some 4-5 advisors, even being called over the phone. No solution other than check your SSD for errors, try another one and so on.

Decided to further experiment, so I plugged the IcyBox in a TB powered hub (the mighty OWC Thunderbolt Hub). Worked like a charm. Decided to take things even further, so I plugged in my small D-Link DUB-M6100. Also plugged the IcyBox and.... wouldn't believe my eyes... it worked.

Since the OWC is nothing to consider hauling around when touring, and the D-Link fits in a pocket, I am at least happy to share this with you, hoping you'll also find it helpful.

From my standpoint, I reckon that Apple has not yet optimized the power delivery via the TB ports in Sonoma and Sequoia (albeit the problem has been around for quite some time now). Hopefully they F***ing Will, because otherwise it could become a laughing stock.

Also, using the USB-A connector of the IcyBox cable resulted in a no-show for the SSD; it looks like only USB-C does the trick.

Clearly a power management issue on behalf of Apple, but something that needs to be reported over and over until they finally fix it.

15.1.1 doesn't solve the problem.

My case : Mac Mini M4 / Os 15.1.1 / OS updated at startup (new machine)

1. OK : The USB HUB of my Benq PD2705Q monitor connected to rear Thunderboldt/USB connectors with a USB-C/ USB-2 type B2 cable permit the connection of all my USB Flash Drives and other USB accessories (cards reader etc.). This Benq USB HUB is identified by System Information as : 5-Port USB 2.1 Hub, Provider Realtek Semiconductor Corp
2. Not OK : Whether connected on the front or rear USB-C Port, my StarTech Hub (USB-C to 3 x USB-A + 1 USB-C) identified as USB2.0 Hub with Genesys Logic ship has a completely random operation.
3. Not OK : Other Startech products (i.e. USB-C to SATA adaptors) do not work directly connected to Mac USB Ports but there equivalents (USB-A to SATA adaptors) works perfectly on the Benq USB Hub...

Remarks :

1. In case of Benq Hub, System informations give the number of ports, ports are USB 2.1, ship are Realtek
2. In case of Startech Hub, System informations do not give the number of ports, ports are USB 2.0, ship are Genesys Logic

Have had similar issues to everyone else. There has been a new OS update Sequoia Ver 15.1.1 (24B91) and it appears to have resolved the issue of mounting any USB device via USB-C dongle