"USB MSC Mode" doesn't work

I’m able to read and write to my SD card both when it’s inserted in the machine and my computer (Mac), respectively. But when connecting a USB cable between the machine and computer and trying to enter “USB MSC Mode” the following occurs:

  1. My computer can’t recognize the machine as a USB device

  2. When hitting “USB MSC Mode” a first time nothing happens, a second time it says “No SD card inserted”. I then have to reboot the machine to be able to read and write to the card again

I have re-formatted the card several times and been trying different cards (SanDisk, Samsung, …) and different cables with the same results.


I am having the same exact issue. No luck so far.

what OS do you have on your computer? Here on on Mojave, I don’t have any issue with this.
The only thing I noticed is that if I eject the drive on the Mac it is mounting back directly. So to remove it securely I have to eject the drive and as soon as it disappears get out the MSC mode on the S2400.

I’m having the exact same issue as well, running macOS 11.5 Big Sur. I’m on the July update and hoping to upgrade to the August firmware but cannot mount via USB MSC right now.

Hey @mxubeats If your mac has an SD card slot(or if you have an sd card reader) you can remove the SD card from the S2400 and put it in your mac and copy the file that way. Im on 11.5.1 and its working here, but until the MSC mode for your setup gets sorted thats a workaround to get the latest OS.

@krikor You do not have to eject the drive on your Mac. Just press the back button on the S2400, and ignore any messages.

Problem with Mac OS Big Sur, is that the drive is recognized, and immediately this eject message appears. The screen on the S2400 just says “Waiting for computer…”


If you exit from the USB disk screen on the S2400, whilst leaving the USB connected to the Big Sur Mac, and then re-enter the disk mode on the S2400, it will succeed. Not sure why this is. Ejecting the disk is also problematic from the Mac OS. It will hang, and usually will give the same disk ejection warning when you unplug the S2400. Not sure how to avoid this on Mac OS.

To those having trouble with Big Sur. Can you please do the following and report back:

  • connect S2400 to Mac directly (no hubs) via the USB Type B port on the S2400
  • boot S2400
  • Go to File menu and enter USB MSC mode
    What happens?
    If the S2400 doesn’t appear in Finder:
  • On your Mac, go to Apple menu / About This Mac / System Report / USB
    Is the S2400 listed anywhere there?
  • Open Disk Utility
    Is the S2400 listed there? If so is it mounted or unmounted (if unmounted it will be greyed out)?

Note: Big Sur is working fine on test machines, so we need to find out if there’s something local that is interrupting the mounting process on your Mac.

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Okay. Following that flow, ie; connect the S2400 before booting it up.
USB MSC mode works fine.

For what it’s worth. I’ve noticed the exact same behavior with the S2400 now, on Mac OS Catalina, and High Sierra. It isn’t an issue that is isolated to Big Sur. It seems to be a general Macintosh compatibility twerk.

An extra step, but at least it’s a solid, repeatable method for accessing the S2400 disk directly in the machine, without needing to eject the SD card.

Thanks @DOS.putin. Does that mean that previously you were plugging in the USB cable after the S2400 (and computer) was booted? And this causes the immediate eject message you mentioned earlier?

Yes rozz3r;

The previous method would be to have the S2400 booted, working on a project when the need to transfer data might arise. Attempts to make the connection were carried out that failed. Since have tried the method previously mentioned, shutting down the S2400, plugging in the USB cable between Macintosh host and S2400, then booting S2400 and entering USB MSC Mode where the drive has been mounted by Mac OS reliably. Ejecting the disk is another discussion and sometimes hangs requiring a “Force Eject”. Going to chock all of this nonsense up as an idiosyncratic behavior with Mac OS and how it handles mounting drives. I do not have the same issue with the S2400 on any of my machines that are running Linux distros (Arch, Debian). Mounting the S2400 on those machines simply just works.

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Interesting, thanks for taking the time to describe. The obvious solution is to leave your S2400 USB cable plugged in at all times, but I appreciate that might not be convenient with your setup. I’ll do some testing on plugging cables in after boot. In theory it shouldn’t matter, but it sounds like it’s causing problems for you at least.

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I’m still experiencing issues with my USB MSC. Additionally, USB Audio doesn’t register at all with my MacOS Big Sur laptop, despite bypassing all hubs and going direct. Anyone else experiencing this?

@mxubeats The S2400 is class compliant so it should ‘just work’, especially on Mac. If you enable USB MSC, then open us Disk Utility on your Mac, do you see the S2400 listed on the left panel at all?

I’m having this issue with one S2400 (earliest run) but not a later one.

No hub, USB-A to USB-B, MacOS Big Sur 11.6, connected before booting.
Latest firmware installed.

USB MSC Mode - Waiting for Computer, does not appear in Disk Utility, does not appear under system report.

If I back out of USB MSC Mode, it shows up under the USB 3.1 Bus and is available for MIDI in/out in Ableton.