Time Machine sparsebundle mount failed in attempt to recover new Mac from backup

There will be complex command line statements you need to run in Terminal. You may need to translate the examples shown to match your precise path and filenames, etc.

First step: Backup the sparsebundle to another disk.

Turn off Time Machine

sudo tmutil disable

Make the sparsebundle read/write by issuing the following command and enter your password when prompted:

sudo chflags -R nouchg /Volumes/{name of your disk}/{name of}.sparsebundle

Next, mount the volume using this command which won't mount it normally but Disk Utility can access it.

sudo hdiutil attach -nomount -noverify -noautofsck /Volumes/{name of your disk}/{name of}.sparsebundle

Then try opening Disk Utility and running First Aid. If that fails to fix it, consider a commercial 3rd Party

https://www.easeus.com/mac/mac-data-recovery/ <-- cheaper and it might work

https://www.prosofteng.com/mac-data-recovery <-- best software on the planet but not inexpensive

It it will still not mount, then you've got a severely damaged sparsebundle that is irrecoverable.

You should be able to mount the disk and navigate the contents of the Time Machine in a read only state. Then copy what you need somewhere else.

Mount via CMD + K Connect to Server

smb://capsule._smb._tcp.local/<Time Machine>

Where <Time Machine> is the name of your Time Machine drive.

Double-click the sparse image and if it refuses to mount then it's damaged. Repairing it is rather technical. Let's jump that hurdle only if you cannot mount the sparse bundle.

Restart your NAS but don't just turn it off and on. There is normally a management interface you can access via a web based admin page. There should be an option to restart the NAS via the admin page.

When it comes back up try it again.

You aborted a restoration process that was working? There might be something mounted, have you attempted rebooting and retrying yet?

I was afraid of that... The sparse bundle is likely damaged. You'll need to see if you can copy any data out of it or decide to just delete the sparse bundle and stop and start Time Machine to create a new backup.

Pretty similar use-case here...

TM on Synology NAS, 6TB of backups have suddenly become unusable ! :(

at first hdiutil reported 4 entries when doing the attach (one of which, the 2nd, was APFS, and not HFS as often mentioned elsewhere), but now I'm getting immediate errors like "Device not configured" or "Resource temporarily unavailable" ???

Same story as you, fsck_apfs reported an invalid object map (1st aid doesn't work neither), and can't solve the problem.

Tried Disk Drill and Mountain, no luck.

Is there any commercial software that could help recover parts of a corrupted TM backup ??? (looked at prmosoft, but corrupt APFS TM partitions seems somehow 'out-of-range' for them, will ask their support...)