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

I have this issue too, but I have it with FOUR drives that are part of a JBOD "Raid" setup. All four will mount properly when plugged into a different Mac, and the Raid works perfectly, but NONE of them will mount on my main machine. These are empty freshly formatted drives put into a JBOD to make it big enough for a Time Machine backup. To me, there is only one word to describe this situation.

PATHETIC.

Apple really needs to get their act together, when it comes to disk management.

The solution I received from mikefromwhitchurch back on 5/8/21 worked for me. My drive is partitioned and 1 segment showed up but Timeline would not mount.

I ran his solution and then used First Aid on the drive. It took several hours (5+) to recover probably due to the amount of data but I’d expect newly formatted drives should take much less time. Give it a try, and run overnight if need be.

Good luck!

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.)

Booted up my machine this morning. YET ANOTHER external SSD has now been affected, this time a Samsung T5. This brings the count to SIX drives, and means that it has hit all but ONE of my external drives. At this stage, I hardly have any data on external drives. I've moved ALL stored data to my NAS.

Am now making sure all my backups are up to date (since Time Machine no longer can be relied on) and putting things in place to abandon the Mac platform for good, as I can't afford to waste time fixing and working around stupid bugs that Apple can't be bothered fixing.

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.

****, we're 2 years further and there is still no answer from apple on this!

I'm having the same issue and did everything that is suggested in this thread, but it's still not working. Apple where u at?

I've had this issue with 2 separate hard drives and I got both to work!! It really is Catalina or what ever OS software you're using most likely. I always find a solution and forget to post it. Ultimately it comes down to just leaving your ex-drive plugged in for extended period of time and it should show follow steps below!

Step 1. Open Finder

Step 2. Go To Applications

Step 3. Go to Utilities

Step 4. Go to Disk Utility

Step 5. Your drive should appeared greyed out on the left hand side under "External"

Step 6. Click on the drive you'd like to mount

Step 7. Click on Mount (should be next to restore at the top under "Disk Utility"

Step 8. You should get an error message click ok

Step 9. Click on mount again you'll continue you to get the error message so rinse and repeat

Step 10. After 3 or however many attempts you've made to mount your hard drive just leave it plugged in

Step 11. Leave drive plugged into Mac and it should mount within 30 minutes or so after your failed mount attempts

Open Activity Monitor > highlight Disk and search for fsck > Double click fsck > click Quit > choose Force Quit, the external drive immediately appeared on the desktop with full access to all files

Tuxera was my only (quick) solution too. My 4TB external ExFat HD 'suddenly' stopped mounting. After reading a couple of possible solutions I did realise it probably happened when the power supply in the street was cut for couple of hours ( I always leave my MacMini in sleep). So Disk Utility did see the disk but couldn't mount it, killing fsck in the Terminal didn't work.

Tuxera (which I happened to have purchased years ago and occasionally use to write to & format NTFS drives) did the job and mounted this very important hard drive (of which I don't have a backup, ouch). Thanks for this tip!

Did you ever find a reason as to why it is doing it? Mine will not stop and I have all of my work on an external. One person stated it wont quickly mount as it could have been removed without being properly ejected. If this was the case, then my SD cards that I consistently forget that my LR hasn't ejected, wouldn't mount as fast. My externals are the only ones that don't mount quickly. Two in particular. I am really getting frustrated as I don't know how to make it stop. I can't access my drive right now and its been 10 minutes. And randomly in the next 30 min it will mount. I'm so grateful I have everything backed up on a non-apple server because this is insane.

Poor or interrupted disk not ejected properly. My MacOS Catalina 10.15.7 upgrade disconnected my external drives and one of the did not come back. All I had to do is kill the fsck_hfs. You may have a different fsck running depending on the type of partition you built. killing fsck will not hurt anything and it should relaunch. You can find it in either terminal and type "top" find "fsck" type running, quit top and type "kill -9 (PID#). You can also find it in Activity Monitor double click the process and click "Quit" or "Force Quit". You may have to enter in your administrator creds. Once I killed "fsck_hfs" the disk mounted and I could run repair on the disk just to be sure the disk was good.

I could not mount my hard disk due to this error :com.apple.DiskManagement.disenter error -119930878

Solution :

1) GO to activity monitor

2) Go to disk tab

3) Quit diskunmountwatch process

Try mounting your disk again, it worked for me!!

I had the same problem. It was caused by the drive being removed without being ejected correctly. I tried a few of the solutions but the thing that worked was actually just waiting like 20 minutes and it eventually sorted itself out. Someone else said it on here but the more data you have on your drive the longer it takes to figure itself out. So I would try giving it a few hours before going into the terminal or buying expensive apps.

Nothing has worked with me. I tried all the solutions listed here except the one from activity monitor because I couldn’t find fsck_ext, I searched & nothing appear. I tried going into safe mode and I can see my drive and mount & unmount it but again didn’t work. Any new ideas?

Open Activity monitor and forse quit there fsck_ext. Will solve issuer.