An external disk refuses to mount, com.apple.DiskManagement.disenter error -119930868.

I tried DiskWarrior. It's really, really expensive, but it mounted my

unreadable hardrives and rebuilt the directories so the disks mount. No

data loss! No guarantees, but it worked for me.

I tried DiskWarrior. It's really, really expensive, but it mounted my

greyed out hardrives and rebuilt the directories so the disks mount. No

data loss! No guarantees, but it worked for me.

force exit fsck_ext from Activity Monitor under CPU tab worked for me!

I’ve since allowed the disk check to run its course (took about 30 mins for 1TB disk) now works without issues.

Since this happened to me using a 5T external WD HD after upgrading to Catalina, here's what I've been experiencing. I've found if I leave the HD attached but not tended to (no activity, photo editing, etc) for a long period of time then I cannot easily eject the HD. I literally have to shut my MacBook Pro down, unplug it, and then restart the computer. When I plug the external HD back in, it does not mount right away but it will after say after 15-20 minutes. Then it works just fine. It's very annoying but I've not found a simple solution to all of this. One thing I make sure to do is use the WD utility and check the drive to be sure there are no issues when I replug the HD.

thank You @Torgash. Your response helped resolve this problem for me. I too ejected an external disk improperly, and was having trouble getting it to mount (on Catalina OS). I had tried several reboots, unplugs, disk utility mounts, but none worked. Then I read @torgash’s response and decided to give it “some time.” I walked away for about 5 minutes and walked back to find the external disk mounted and running properly. It seems in this case, it may be worth giving it some time......

An external disk refuses to mount, com.apple.DiskManagement.disenter error - 0

I just cold-cut turkey pull the USB chord after many failed tries to mount unsuccessfully and when I plugged it back in it worked and I was able to retrieve all my data, IT WORKED!

Catalina doesn't recognize the exFAT format anymore.

I had to sacrifice my old backups on my 1TB external HD, and erased it using disk utility. I used the recommended format and it works now. Good think i still have my other external HD that had the same info which I connected to my old laptop.

It's frustrating indeed but that was the only solution that worked for me.

I've been having this same problem lately. Some times it works and some times it doesn't. And I've got the highest spec 16 inch Macbook Pro available (yes everything including hard drive spec'd out to the max)

The external USB hard drives (SSD and non SSD) and USB thumb drives I'm trying to mount are varying between exFAT, MacOS Journaled, FAT, AFS. I don't have NTFS formatted drives. And not a single hard drive or USB stick or SD card will mount. At all.

Below is a summary of things that didn't work for me, and things that I thought worked.

Here are things that didn't work:

• Using Terminal or Activity monitor to find fsck_exfat or hfs or any variant of it and killing the process: This didn't work because these processes were not running, and wouldn't show on any of the tabs in Activity Monitor, nor could I find the PID or process of it using Terminal.
• Free Version of Microsoft Tuxera NTFS - didn't work
• Free Version of Paragon NTFS for Mac - more on the Paid version below
• Relaunching Finder by killing it: nothing happened.
• Using diskutility to run Firstaid or even Format and Erasing a drive - tried this on a couple of drives i was okay to sacrifice the data on... and nothing.

Things I think contributing to the issue:

• Sophos Antivirus. As pointed out by someone this could be the root of it. Sophos also plays havoc with Dropbox/GDrive/OneDrive finder mini status icons, but I digress. Unfortunately I can't turn Sophos off, as it's a company owned machine, and despite me having sudo/admin access I've been told off before for disabling/removing it.

What i think worked:

• Installing a paid version of Paragon NTFS for Mac. I had the license on an older machine, had to use it a couple of times when using other colleague's drives that came NTFS formatted. And i had only used the free version to see if it fixes this issue. I added the license into the free version, restarted and voila! i could access all kinds of drives! exFAT, Mac OS Journeled etc etc.
• Restarting the machine. Maybe Paragon NTFS did nothing? and maybe it was the restart. Though i restarted a few times before this, and nothing happened before. It's hard to say.
• Waiting it out. As it has been suggested a few times on this thread, maybe it was the fact that it so happened that my drive was plugged in for a long time and after installing Paragon NTFS and restarting that it decided to work? it's hard to say.

This has happened 3 to 4 times for the last 4 or 5 months. And i keep googling for answers and come to this thread all the time. Keep trying every single suggestion and meet dead ends. But something i do fixes it and on i go.

I hope someone can actually get to the bottom of it and provide a definite solution, and maybe the cause of it - so we know what to watch out for.

The reason for this is that Apple removed support for HFS file system in MacOS Catalina.

Various options exist to access CDs, HDs or other images with this file system.

For a discussion, see:

http://www.matthewhughes.co.uk/how-to-mount-hfs-classic-drives-on-macos-catalina-and-later/

and

https://apple.stackexchange.com/questions/389186/reading-hfs-standard-and-mfs-on-catalina

I have 3 different external drives 2 Seagate and 1 Western Digital. My macbook pro keeps disconnecting them for some reason and they don't eject properly. I was able to get all 3 working again by simply rebooting the mac and waiting. Not really sure how long it took, but it did reconnect by the end of 3 hours.

If you can't wait, you can always connect through a windows box OR through a network router that has an external disk attachment. This process has worked every time for me and I use only ExFat formats for my disks.

Hth :-)

Sadly, First Aid didn't do much, as the problem was specific to one machine. I ended up splitting up the group of disks and backing up my data using a third party program called Sync Folders Pro. As I did the backup, I noticed that the drives were very slow. Checking on the speed, I discovered that they were operating at only 30 Megabytes a second. Normally, they work at 140, so this is a significant slowdown. I checked the hub they were plugged into, by speed testing an SSD, and that was fine. In the end, I had to do the backup one drive at a time, with the backup and source drives plugged directly into the machine and swapping them as required. That was the only way to get them back to full speed and have the backup take 2 days, instead of more than a week. The reason for the slowdown and the drives refusing to work together remains unknown, but with only having 2 USB ports on my Mac Mini (and 4 Thunderbolt ports), there is no way I can plug all the drives in directly. With so few ports, they are needed for other essential devices (like my eGPU).

On the good side, the backup was completed, even if it wasn't via Time Machine, and I have a NAS due to arrive tomorrow. To me, a NAS is the only real solution to the ongoing issues with hard drives that macOS has (lack of ports, random disconnections, slowdowns, disappearing drives [that are mounted but don't show up on the desktop], random disk errors, permission problems, etc.)

Tried that, didn't work. Couldn't even reformat the latest drive using using Disk Utility. It refused to do it. Plugged the drive into a Windows machine and reformatted it there to NTFS. Then plugged it back into the Mac and Disk Utility was able to do its job. Then recovered the drive (it was full of cloud data, so nothing lost). Not the first time I've had to do something like this, as this SSD was a replacement for an earlier drive that was rendered irrecoverable by the same bugs. I'm just glad the new drive is still usable, but I'm well aware that all external drives are now at risk and can be rendered inaccessible at any time. Have already transferred as much data as possible off external drives and onto my NAS. Drives with data that is not used every day, I have unplugged from my machine so the OS can't affect them.

Open Activity Monitor and type in "fsck." If a process is shown, force quit it, the drive should now show up in Finder.

How are/were the drives formatted? If they were NTFS then the upgrade removed the software required for that format and will have to be reinstalled.