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

1. Go To Disk Utility
2. Select External Drive
3. Press “Erase”
4. Name the Drive
5. Format as MacOS Extended (Journaled)
6. Leave “Scheme” as is.
7. Click Erase 

I was able to solve the problem by entering the activity monitor and forcing the finder to close

It really help me. Do no remove hard disk directly. If you directly remove then mac will unmount the hard disk for system. Goto disk utility and click mount or first aid option.

This worked for me also, I found I had to do this every time I used the drive.

I left the fsck to run its course (about 30 minutes for 1TB) and the disk works correctly every time now.

That worked for me. Opened Activity monitor and force quit fsck_ext. Thank you so much!!

Hey all,

I found a fix for this.

update dyld shared cache -force

reboot in safe mode

reboot again normally

It worked of 4 computers for me so far

Let me know if it works for you

I am not agreeing with wrongly ejected position. This clearly a kext file disrupting the usb mount. If you boot in safe boots it will mount. The big question is why and which I extension is it.

In my case, it took a lot of time. I finally ended up letting my external drive run all night and it was mounted in the morning. I don't know how long it actually took to check a 2TB drive, but after ejecting it and connecting it to a new iMac with Catalina, Migration Assistant is doing its thing. Patience is the key.

@roman127 right...even though I called the apple support and they claimed it is something to do with my drive. They said they could send me to Seagate support. I didnt think it was anything to do with Seagate but I tried going through Seagate's website. It looks like they have a data recovery app called pixel8 and it could read my drive, just wouldnt mount but it discovers the files I have in the drive. It will cost $99US for a year of subscription to recover my HD. I wonder why they came up with this software pixel8. I also found out that Seagate does not have a lot of support on Mac side. On PC side they have firmwares and softwares. So I am not sure what the problem between Seagate and Apple is, not supporting each other. For customers, we are in the middle and cant get our problems solved.

Initiate Terminal mode.

At prompt, key first command and hit return/enter:

[user]$ ps -ef | grep fsck

You should see something like the following, the first three bytes from which is the PID:

  501   680   653   0  2:55PM ttys000    0:00.00 grep fsck

...Now at the prompt, you key the second command with the applicable PID:

[user]$ sudo kill 501

It might work for you (I hope it does). It did not solve my issue, and tainted disk still won't mount and I continue to see the same error as OP.

You're great SAL0808!!!

I did what you suggested about downloading and installing Windows NTFS Tuxera and after the installation, the system was restarted and the external disk came to life !!!

Millions of thanks my dear, I really love you.

mac1317's help worked when I had a disc that wouldn't mount..... now just helped my Time Machine disc that I was error checking with Disk Utility. I did this before and it took over an hour but sorted itself out and I eventually could press "done".

Not today, started, went out, came back 4 hours later and it was still "checking catalogue" (or something!)

Opened Activity Monitor and there at the top of the process list was ....... consuming a whopping 3+ Gb of memory!

Killed it, Disk Utility immediately said it had failed to verify or repair disc but at least I could get out of it!! Just checked this disc, all info still there, Time Machine working OK so no harm done.

However, that process needs looking at!

[Edited by Moderator]

Thank you for all your helpful comments. After two hours of wasted time, I found this forum. I tried Tuxera and it did not work for me but killing the fsck_* in activity monitor has seemed to work for now. This is ridiculous and should be addressed by Apple.

for some of you downloading Tuxera (and paying for it), I would look into getting Paragon Software, on the Seagate website. I would assume It works with only Seagate drives, but it fixes the issue for free. I was also able to mount one of my drives that was greyed out in Disk Utility. Hope this helps!

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!