External drive not mounting after Sonoma update

This is exactly what happened to me. And I'm blaming exFAT. Everything had worked fine before I upgraded to Sonoma. What I had to do: Used EaseUS software ($100/month), recovery software recommended in MacWorld...it performed a miracle for me. It let me get into the exFAT drive even though it would not mount. Took a long time...like 10 hours to scan 10TB...but I could see my files! You do need to do more than just copy the folders to another drive...the folders come across empty. So you have to look for individual files and then copy them over. I had FCP video projects and was able to recover all the video clips. The recovered fcp.bundle says it was damaged, so I'll probably rebuild project using a backup fcp.bundle that's was stored in my Movie folder on the desktop.

After copying files over, I am changing all my mechanical external drives from exFAT to APFS.

Apple: I think this is a major issue with Sonoma that needs fixing.

I called Apple. Nothing they can do. Engineers "aware" of reports. Work around is to plug in to Windows computer, scan and repair drive... plug back into Mac... It will then mount (until you eject and go to plug back in - then it WON'T MOUNT)... so transfer over to a new HD formatted as APFS... That's what we need to do. It's a JOKE.

I don't know if this is an exFAT issue. I have the same situation with a WD Elements 5TB drive, formatted as APFS that worked just fine until at least 2 weeks ago (according to my Backblaze missing drive message), and I am getting the same error message. I suspect it's an issue with macOS being aggressive and not letting external accessories connect without permission, as I'm also having issues with my external display refusing to reconnect after waking from sleep. Whatever it is, it is maddening.

I have the same issue with my RAID system no longer mounting in Sonoma. Did you find a workaround? My external hard drives can be mounted, just not my RAID system. It was actually working fine yesterday until the software update last night.

Yup had this same thing happen to me. “Fixed” the drive in windows and then mounted it just fine on Mac until I attempted to unmount and then mount it again. Back to the same issue as before and the workaround of using windows to “repair” the disk no longer works. Such BS.

Have similar issues. flash drives with GUID won't show up on my iMac with os 14.3.1 but will with my MacBook Pro with os 14.2.1. I am afraid to update MacBook Pro at this time. Could be the iMac or the OS, not sure. I will have to do more digging.

Grebrednav wrote:

I migrated from a Mac Mini to a new 2023 Mac Studio Apple M2 Max yesterday and then updated the OS to Sonoma 14.0. Now one of my drives, a 36tb OWC "Gemini" external HDm formatted ExFAT, will not mount. It worked perfectly before the migration and still mounts just fine to my MacBook Pro. In fact, Disk Utility on the new Mac Studio sees the drive but will not mount it, giving error message "com.apple.DiskManagement.disenter error 49244"

I have seen several other posts on these forums where people reported issues with their external drives formatted as exFAT after the Sonoma upgrade. Not sure if it is an issue regarding exFAT or whether it is a drive issue.

What do I have to do to mount this drive?

Try connecting the drive directly to the Mac.

Try disconnecting all other external devices in case one of them is causing a problem. A couple years ago I saw numerous posts where some external drives were having issues when connected to an Apple Silicon Mac and running Monterey....turns out a third party external device was causing the problem.

Try booting into Safe Mode to see if that makes any difference.

Have you tried running Disk Utility First Aid on the external drive? Even if First Aid says everything is "Ok", click "Show Details" and scroll back through the report to see if any unfixed errors are listed.

Perhaps it may be possible to mount it as read-only, but this would require use of the command line and will be a bit tricky to explain so will leave that option for later.

Are you using a software RAID for this external drive or using the enclosure's hardware RAID?

Are you using the OWC software for this drive? If so, then that software may be the issue. See if they have an updated version available which is compatible with Sonoma. You can also contact OWC tech support for assistance since they have great tech support.

I cannot reformat it- it contains 20tb of precious video content.

No, you don't wish to reformat which is different and is understandable due to the amount of data involved.

Do you have a good backup of the data on this external drive? If not, then you need to do so now if you really value that data. Even external media needs to be backed up if it contains important & unique data (this includes the cloud as well).

I have 2 external LaCie drives one SSD one HHD mounting behavour is erratic to say the least. I have a Mac Mini M2Pro 2023. Upon reading this discussion I decided to check under system settings,general , system report, hardware, usb I could see both drives as initialized as APFS, Partition Map Type: GPT (GUID Partition Table), however this worried me File System: MS-DOS FAT32 is this what really is beneath Apple's new file system or am I delusional.

holtynq wrote:

I decided to check under system settings,general , system report, hardware, usb I could see both drives as initialized as APFS, Partition Map Type: GPT (GUID Partition Table), however this worried me File System: MS-DOS FAT32 is this what really is beneath Apple's new file system or am I delusional.

No, there is a hidden EFI (aka ESP) partition which uses the FAT file system and is meant to be the location for bootloaders on UEFI systems. Typically these ESP/EFI partitions are only 200MB to 500MB in size depending on the OS.