Cannot transfer files to USB / USB is not recognized

What format is the USB drive? APFS (for SSD) or MacOS Extended, GUID (for HDD) recommended. Or maybe exFAT (MBR) if that drive MUST be used with Windows or Linux, but that format might not be so robust.

Also do NOT use any 3rd party virus apps or "cleaners" which often cause obscure errors and corruption -- macOS built-in security is all you need.

Chloe09 wrote:

I have a 2021 Macbook pro that has been updated to Sequoia. I am a photographer, and have always used the same USBs from the same company to share photos with my clients. Recently, I have not been able to transfer my files to the USBs. I have the files in a folder on my desktop. When I insert the USB, after renaming it (like I have always done) I attempt to copy the files from my folder on the desktop to my USB. It will begin to copy, get a few MB (out of a few GB) into the copying process, and then freeze. There is no way to make it continue to copy or to stop without removing the USB. Once I have tried this process on a USB, the computer will no longer recognize that same USB if I attempt to connect it again. It does not show up in Disk Utility or anywhere else on the computer. I have tried this with 12 USBs now and no luck. Any ideas?

a single failure sounds like the USB thumb drive has failed.

does not explain: "I have tried this with 12 USBs now and no luck"...

Did you try simply shutting down and restarting more than once since your: "I have a 2021 Macbook pro that has been updated to Sequoia." Always advised

if no resolve—

A SafeBoot Start up your Mac in safe mode - Apple Support will sort many anomalies

Does a quick disk repair before it fully boots up, and certain system caches get cleared and rebuilt, third party system modifications and system accelerations are disabled temporarily.

Login and test. Reboot as normal and test. Caches get rebuilt automatically.

This will also test if third party interference; most extensions etc are not loaded in safe boot mode.

The current stable release of Sequoia including bug fixes, security updates is macOS 15.6.1

Keep your Mac up to date - Apple Support

Keep your Mac up to date - Apple Support

Chloe09 wrote:

It is FAT32. I have used these drives for many years with my MacBook pro and have not had an issue. A few days ago I reformatted one to MacOS Extended and it still would not copy....

Why do you use FAT32? For one thing FAT32 max file size is 4 GB so you can not copy movies larger than that to such disk.

Besides, FAT and exFAT are not as robust as APFS and MacOS Extended (Journaled, GUID).

If also MacOS Extended fails, then maybe that USB drive is broken.

Chloe09 wrote:

Thank you so much for your response. I rebooted in safe mode and then restarted. I inserted a brand new USB and reformatted it to MacOS Extended GUID partition, and was able to copy a folder to it! Success!

BUT, now all of the other USBs I had tried before will still not be recognized by the computer. When I insert them, they do not show up anywhere on my computer or in my Disk Utility.

Do you think they were somehow broken? Or is there a way that I can access them to reformat them?

re: I have a 2021 Macbook pro

Verify your Settings —toggle some changes here, then come back to Always and compare your results.

Chloe09 wrote:

BUT, now all of the other USBs I had tried before will still not be recognized by the computer. When I insert them, they do not show up anywhere on my computer or in my Disk Utility. Do you think they were somehow broken? Or is there a way that I can access them to reformat them?

It would be weird but not impossible that many USB drives would be broken at the same time.

Were all those USB drives also formatted as FAT? Or maybe as NTFS which Windows uses? A shot in the dark, but if they were NTFS and if you have installed some 3rd party NTFS add-on, then maybe that install is now too old and incompatible so those drives fail?

Unfortunately Apple makes this more difficult than it needs to be. By default Disk Utility hides the physical drives from view. Within Disk Utility you may need to click "View" and select "Show All Devices" before the physical drives appear on the left pane of Disk Utility. Make sure you select the physical drive to erase. Whether you use a GUID partition type or MBR partition type depends on where this USB stick will be used. If it will be used only with another computer (OS does not really matter in most cases), then I usually stick with GUID partitions. If, however, you will be using that USB with a car, TV, or other such device, then use the partition type that device (car, TV, other) requires.

Now, some drives can get into a state where even erasing the whole physical drive is not enough to allow it to work with macOS.....or perhaps the physical drive is not even seen in Disk Utility. In that case, the best thing to try is using a Windows system to delete all partitions on the drive by using the Windows Disk Management Utility. Once all partitions have been removed, you can try creating a new single partition & whatever file system......you will be using Disk Utility to erase the whole physical drive again once you connect it to the Mac just to make sure the drive has a file system Apple has created & understands (FAT32, exFAT, or Apple's own file systems).

If you are familiar with the command line, then it is also possible to use the command line to write zeroes to the beginning of the drive to destroy the partition table & make the drive appear blank. Disk Utility is usually happy with this as well in order to allow the blank drive to be "erased".

It is also very possible you have some bad USB sticks. Unfortunately the quality of USB sticks is extremely poor which does not help matters any.

FYI, it is always recommended to erase the whole physical drive of any new drive you acquire. Manufacturers can place some odd partition tables, file systems, and even hidden data on their brand new drives. Sometimes this hidden data within the partition table can negatively impact the OS and some disk utilities.

Edit: Also, erasing the whole disk can sometimes allow you to detect whether you may have received a fake or worn out/failing products. Unfortunately there are many scams within the various third party marketplaces where this has become more common.