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

I had the same problem on a drive that was partitioned into a data section and Time Machine partition. Pretty new drive and onlh one partition pulled the error and would not mount.

I solved it by "viewing all devices" in Disk Utility then running first aid on the whole device. For a few seconds the partition was still red (ng) but after toggling view it is all good now.

I think the device was ejected "by hand" and the Time Machine might have been in the middle of a back up and so the system threw up.

Try this fix, it is scary to run First Aid on the whole drive, but it worked.

Yeah, this thread is 12 pages long. You'd think that someone from Apple would've responded by now. I feel your pain Getaway Driver. I do video and have video files on separate hard drives. So it's a lot of in/out every day. I had to buy a piece of unreliable Microsoft software to fix my issue and shouldn't have had to. This is really unacceptable. Plug n' play Apple. Shouldn't be that hard to do!

From what i read i literally did what a few suggested which is to leave my external hard drive connected. I left it on over night and miraculously in the morning i now see the external hard drive. Hope this helps!

You do so how ridiculous that is though, right? If I'm on a project and I need access to files at that exact moment from a hard drive, with your solution, I'd have to wait overnight before I can access the files? That's just NOT ACCEPTABLE. EVER. Not in any work environment I know of.

I'm going to try leaving it in overnight, but at this point I think my next computer is going to be a Dell. I can't believe that Apple is just ignoring this problem.

Unfortunately the fsck process does not seem to work for me as I cannot locate this function in the Activity Monitor.

ABSOLOTELY.

Tuxera is the way to go.

If the issue is exactly as is being discussed out here - then this is the one stop solution.

Just a few minutes and it has resolved it - in a snap!

Thanks guys. Ever so grateful.

Had lost sleep over it last night .... !!!

So here is my rendition of the "My drive won't mount on Catalina and..." posts that have stacked up nicely in this thread.

So I'm running a 12 tb 4 bay media sonic raid 5 to back up video and photo work. I backed up my back up to a JBOD earlier in the week and all was well. Then I decided to shuffle some media around, end goal being to move a few things back onto 12tb array. Decent amount of files, I'd say like around 1.5 tb. So I set it forget it and let it do it's thing overnight. When I check in the morning my system is frozen. The transfer errored out and I panic, instinctively tapping the caps lock button hoping to see the green light blink on then off. The only vital sign I can check before doing the much dreaded hard shut down. I do the hard shutdown, fire it back up and the array will not mount. I tried the whole Kill the "FSCK" in activity monitor, this did not work. I've also heard rumors on here of people hooking the "unmountable drive" up to a system running a different OSX. I am running a dual boot with Catalina on one volume and Mojave 10.14.6 on another. I am currently typing this post from Safari on the Mojave volume as I stare blankly at disk manager and the greyed out drive (array) which is yet to mount.. I supposed I will "give it time" which was also mentioned in this monumental thread which has yet to be addressed by anyone from apple. I'll check back here in a few days with an update but if you're any where near as optimistic as I am for a fix on this, you won't hold your breath.

Nothing wrong with holding your breath & waiting. That’s all you can do for now.

Has happened to me a number of times when on boot up, the HDs were not seen on the desktop. Tried all sorts of remedies. Nothing worked. Resigned to fate !

Mysteriously, after some time, up to an hour or two, or even the next day, the HDs reappear.

Happened both in High Sierra & Catalina.

I have no idea what happened.

Have faith. Good luck !

Hi, I installed this app for ntfs drive, even though its not formatted as ntfs, and now i can see the drive again, and hopefully save my data to another drive with raid5 or better for data redundancy, https://www.seagate.com/gb/en/support/software/paragon/

Thanks mate.

this worked.

seems like disk repairing was running in background. When i killed the task a msg popped up - mac os can’t repair the disk but you still can read and write the data into disk and it mounted.

however. Everyone reading this please make sure you safely remove your external drive every time.

this caused me a failure of seagate hdd and Seagate couldn’t retrieve the data 🙁

This isn't responsive to the issue. Those reporting this problem have not changed their external disk drive configuration; what has changed is Catalina or an update within Catalina. i have the same issue, repeated questions to the community have not resulted in answers. A trip to the Genius Bar resulted in my machine being tested, declared to be OK hardware wise, and returned to me wiped with a four generations-old operating system installed and a split Fusion configuration that I had to fix. There's a problem here, and Apple needs to recognize it and develop a fix.

Update on my previous post. I left the drive in for 72 hours and it still did not mount. I have also never seen the fsck process appear in the Activity Monitor. The most recent Catalina update has also not fixed the issue.

This is beyond ridiculous.

Apple, why will you not at least tell us you are working on a fix?

I am on an early 2015 Macbook Pro.

Hello!

I had the same issue with a new drive I just bought. This solution only applies if it is a new drive with nothing in it!

Go to Disk Utility

Select the drive in question

Click "Erase"

This will of course everything you have on the disk but it will mount and appear on your desktop!

So here I am again, a couple months after my original reply in this thread. Raid still won't mount. I found and tried all this stuff. Can confirm this does not work either. It's a bunch of terminal commands to mount and unmount drives. Terminal said the process timed out. I did it a bunch of times.

https://osxdaily.com/2013/05/13/mount-unmount-drives-from-the-command-line-in-mac-os-x/#comments

I can confirm that updating to MacOS Big Sur did not fix the problem. I guess I will be looking for someone with a pre-Catalina version of MacOS to mount the drive. I can also confirm I am switching to PC.