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

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.

I will try that... I looked for the fsck_ext someone suggested in the Activity Monitor but it is not there. I can see the HD, however, it is not mounting. I dont know what Apple did, Catalina was not helping me in a bad day. Very annoyed but was experienced enough to notice it was the update of iOS and not an issue with my HD.

Thank you but I just tried and it is still not mounting, it shows that it is there but grey out. I tried manually mounting and even reversed my iOS but it is not mounting. I am starting to wonder if it was the HD itself... it would be a pain to loss all files!

Have the same issue with my external drive on my MacBook Pro

com.apple.DiskManagement.disenter error -119930868

The drive cannot be mounted in OS Catalina (10.15.1), drive is APFS 3TB HDD. Disk Utility shows it greyed out and if I try to mount it I get that error.

I tried to plug this drive in my friend's iMac with Mojave 10.14.6- it works just fine! Does anyone know how to make it work with Catalina?

This is really interesting..I did a bit of investigating myself. Seems like while Catalina starts, codes like "fsck -fy" would be running in the background to determine if a drive is mounting or not. I wonder if something is missing in those codes that disallowing some external disks be read (My HD is Seagate - 3TB - NTFS) or there is a link between Catalina's security code that sends a signal to your antivirus software saying that, the drive is a virus and should not be mounted. I suspects that because I formatted my Mac and it was under OS X Lion, whenever I plugged my HD in, a window of my antivirus popped up and said "blocked autorun.inf because it was infected with INF: Autorun-BH(Wm)" and I am back to Catalina with the same computer, there is no message when I plug in my HD. Yet, my drive is grey out from the list. All of my other WD drives are ok in Catalina.

My Lacie 2TB portable hard drive suddenly couldn't be mounted on my Macbook Pro (Running Catalina) after it shut down because of low battery power. When I restarted... nothing. I tried to mount it on my MacPro, (High Sierra), same thing and I freaked.

After reading here that all I had to do to restore it, is wait, I didn't think it could be that easy... but it was. It took about an hour, leaving the drive connected before the computer could mount the drive. All is good.

Now I wonder what affected that @dhbaker. I mean, one second it is working and after the update, it has to take an hour to recover the drive. I have a few 3TB drives and they are all mounted quickly (all WDs). I found out that Lacie is owned by Seagate and so they use Seagate's drive. The drive I could not mount is a Seagate! coincident?

@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.

So I think I will also contact Apple Support regarding this issue. But I have really strong argument here- my Seagate drive mounts and works ok with Mojave, so they won't be able to tell me that this is the problem with my drive.

Excellent. Great idea @roman127. I need to reverse back to Mojave and see if it would work. It is a pain because I just got back to Catalina from X Lion. I think I will try a time machine method to backup this computer.

OK, first off I'm quite a junior when it comes to Mac's. However I got this issue resolved. I did the the convert to APFS system as it seemed to be the "smart" thing to do. However the drive showed out grey. I couldn't mount or erase or restore, just nothing. I believed that in the conversion the drive would be partitioned. It was not. After a call to Apple Care they determined they didn't know what the problem was either. After the call I tried the partition option. Problem fixed in 10 seconds. I don't know if that's the issue but it worked for me. Good luck!

Running OS Catalina on a new MacBook Pro. I just had a drive fail on me (WD 2TB) after mounting quickly for the past 24 hrs. Did not eject it manually - literally the drive unmounted itself while I was adding a Word document to it for backup. Other drives I own work fine (WD and Seagate), I could open the drive great on a windows PC, and a recovery app found the documents while loaded onto the problem Mac. The fsck command was not running in background, per activity monitor. So now I'm recovering my recovery drive on a second backup until this temper tantrum fixes itself.

I don't think it's just a Seagate thing, this definitely seems like a Catalina thing.

I'm pretty sure it's a Catalina thing. I formatted my Seagate 5TB drive with exFAT on Windows, my Mac didn't mount it. My other WD usb drives with NTFS are fine. I reformatted the Seagate with NTFS, Mac has no problem mounting it, of course I can't write to the drive. It looks like Catalina abandons exFAT, sad!

I had another disc give that error (dissenter error) and this time the fsck_ext didn't show up in Activity Monitor. It wouldn't mount on the iMac - so I plugged it into a PC and formatted it ExFat from there no problem, and it now works on the Mac.

Interestingly I ran into the same issue with my new MacBook usb-c and Catalina. After I accidentally unplugged the external drive (sometimes it just removes itself, probably due to power issues) I can't mount the drive anymore. Its a portable 4TB WD drive USB3 with extfat. If I mount it on Linux on another computer it works again. It's a nasty workaround but it works for me.