Mac OS Sequoia not recognizing USB Flash Drives

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

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. Especially for someone like me, who has a very basic understanding of how tech works. Trogander, you lost me on step 3 but I do appreciate all the detail you provided.

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.

In Terminal, type the following:

ls /dev/tty./*

If you see something like /dev/tty.usbserial-xxx it may have found the USB port but can't communicate with it, if that makes any sense.

The xxx would be th port number

UPDATE

Bought the new OWC Express 1M2 and it works at a fantastic rate.

Both read and write are well above 3000mb/s. So it was a defective enclosure of some sort. But rather odd that it worked on all of my older OS X systems...

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.

Sequoia also fails on both intel iMA and M1 macbookpro, when copying very large folders (with thousands of files), with error 50, every time. However on a Sonoma macbookair it works every time, for the same folder, on the same drive, on the same network.

My drives now auto-mount about 100% of the time after a re-boot.

Does macOS Sequoia go through some type of "learning process" where it learns what drives it needs to mount?

I'm on 15.1, but I did not see any improvement when updating to 15.1. I only saw improvement after a couple weeks of reboots.

One more for the pile:

My mother bought a new Embroidery Sewing machine and it takes USB thumb-drives but only in FAT16 or FAT32 format.

So Now I've discovered that for whatever reason, I cannot get her 2019 5K iMac which is running macOS Sequoia 15.1.1 to mount any FAT16 or FAT32 USB drives. It can even format usb drives with these formats in Disk Utility and then Disk Utility will give an error that it couldn't mount the disk afterwards.

I can mount ExFAT or macOS formated USB drives on her iMac just fine... but of course those aren't supported by the sewing machine.

To top this off, my Aunt is visiting and had her M1 MacBookAir running macOS Sequoia 15.1 and it *can* mount any and all FAT16 or FAT32 USB drives I throw at it. Also, my 2022 M1 Max Mac Studio running macOS Sequoia 15.1.1 can mount any and all of these FAT16 and FAT32 formatted USB drives too.

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.

I feel like every new major release of macOS just comes with more awful bugs that never seem to get fixed with later releases.

I have a different problem - my USB flash drive loads just fine, but it's always UNTITLED as the name - and I can rename it and it won't hold the name after I pull it out and reinsert it. Every flash drive I have does this. Load that flash on another Mac and the name is always there. This is on an M3 and I just updated to 15.2 and it still does it.

I’ve replied elsewhere? But- click ‘about this Mac’ system info >USB> and ‘if’ it’s there click on the drive for a pop up asking for permission.

after the first instance, the pop up has appeared when I connect another drive once or twice, but they aren’t hiding anymore- it didn’t appear in Disc Utility originally either.

they don't but oddly my external hard drives and iPad show up with no problem, so that's why I checked my devices on other computers to make sure it wasn't the usb drives or midi devices that had an issue, and they work perfectly fine on other computers that don't have the sequoia 15.2 update

I just purchased a new MacBook Pro with M4Pro and it has Sequoia 15.3.2 and my USB flash drive will mount fine.

I just upgraded my MAc Studio with M1 Max to Sequoia running 15.3.2 and that same USB drive won't mount. I am using USB-C.

Luckily the Mac Studio doesn't have any problems with my ProGrade Digital CF Express readers and my 2 External G drives. They all are using USB-C.

Tueso wrote: "Have any of the apple support team seen this post?"

Doubtful, considering thousands of daily posts and these being user-to-user communities. Use this form:

Feedback - macOS - Apple

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Interesting-this article Use the ports on your Mac - Apple Support

does specifically say “laptop”…

Strange, all USB drives show up fine here in Sequoia 15.2

Are you running any VPN, Anti-Virus, or Cleaning apps?

We need to see what all is running, a report from this will not display any personal info...

Using EtreCheck - Apple Community

EtreCheck is a FREE simple little diagnostic tool to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac. It will not display any personal info.

https://www.etrecheck.com/

Thanks for Old Toad’s etrecheck instructions…

Slow iMac 2017 - Apple Community