After a reboot I am unable to mount an external USB-C SSD with Catalina 10.15.5

Disk Utility is recognizing the disk, I can see a "disk3" container with my APFS volume , but once I try to activate it I get a com.apple.DiskManagement.disenter error 49218

When trying a diskutil repair I get :

Started file system repair on disk3s1 1TB - SSD
Repairing file system
Volume is already unmounted
Performing fsck_apfs -y -x /dev/rdisk3s1
Checking the container superblock
Checking the space manager
error: (oid 0xa550) cib: invalid o_cksum (0x0)
error: failed to read spaceman cib 0xa550
Space manager is invalid
The volume /dev/rdisk3s1 could not be verified completely
File system check exit code is 0
Restoring the original state found as unmounted
Finished file system repair on disk3s1 1TB - SSD

But disk still cannot be activated afterwards.

I already tried disk utility from recovery mode, no success... Also tried to connect the disk with another USB-C cable with no success...

The disk is 4 months old and worked initially. What are my data recovery options?


1 Answer 1


There is an app called Mountain that I use to mount stubborn drives. It has worked well for me. The app is not free but has a free trial. You can get it from this link.

  • Didn't work. For people discovering Mountain (as I did), their is a similar open-source app ejectify.app
    – gagarine
    Commented Feb 12, 2022 at 18:17

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