Time Machine "Backup Not Completed" error for LaCie SSD

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Level 1

25 points

Time Machine "Backup Not Completed" error for LaCie SSD

I seem to be unable to consistently initiate a manual Time Machine backup to a LaCie 2TB Mobile SSD Secure external drive. I connect the SSD, unlock it through the LaCie/Seagate Toolkit, then click on "Back Up Now" under the Time Machine menu. A few moments later, a "Backup Not Completed Time Machine couldn't back up to "LaCie"" error message pops up. Clicking on the error message's "Details" button launches System Settings, which shows an additional error message of "Time Machine couldn't complete the backup to "La Cie" An error occurred while preparing the backup". Is there something I'm overlooking, or a workaround?

[Edited by Moderator]

iMac (M4)

Posted on Aug 22, 2025 04:22 PM

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Answer 1

Aug 22, 2025 04:40 PM in response to SJBertorello

SJBertorello wrote:

I connect the SSD, unlock it through the LaCie/Seagate Toolkit

Don’t use the 3rd party tools.

Use Disk Utility to Erase the drive, format it as APFS, not encrypted. When the process is done, go to System Settings > General > Time Machine and set up the blank drive as an encrypted TM backup.

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Answer 2

den.thed

Level 10

88,804 points

Aug 22, 2025 05:04 PM in response to SJBertorello

The SSD may not be properly formatted or the LaCie/Seagate software is blocking Time Machine.

To fix that problem open Disk Utility, then Ease and Reformat the LaCie drive to GUID/APFS.

as per > Initialize an external storage device in Disk Utility on Mac - Apple Support

Once that's done, you should be asked if you want to use that external drive for Time Machine Backups.

see > Back up your Mac with Time Machine - Apple Support

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If that doesn't work..?

Then you may have a problem with some third-party Anti Virus or Protecting software that is installed on the Mac.

EtreCheckPro is an excellent tool for finding and sorting out various problems.

Download and run the free version of EtreCheckPro, from > https://etrecheck.com/en/index.html

Then post back here with your Report, as per > How to use the Add Text Feature When Post… - Apple Community

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Answer 3

Aug 23, 2025 01:51 AM in response to SJBertorello

Time Machine tends to be picky about formatting. Try erasing the LaCie in Disk Utility, set it to APFS (not encrypted), and then let Time Machine handle the encryption when you enable it. If the problem continues, double-check whether you have any third-party antivirus or monitoring apps installed, since they can interfere.

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