Fixed: Time Machine Backup Fails After Updating to Sequoia

Time Machine backup fails after upgrading to macOS Sequoia and continues on macOS 15.0.1, especially when you take Network Attached Storage (NAS) devices as the backup disks.

Here's a true case:

What make Time Machine backups fail on NAS devices after upgrading to macOS Sequoia? I've checked the network connections and Firewall is enabled and stable on my MacBook Pro. However, the backup is no longer working if I back up my Mac to a NAS device with Time Machine. - a case from the Apple community

This is a common issue on macOS Sequoia but not an insoluble one. Here, we'll help you analyze the error message you receive when Time Machine backup fails and offer ways to fix it.

Time Machine backup fails after upgrading to macOS Sequoia, how to fix it?

Since the update to macOS Sequoia, Time Machine backup hasn't worked. It makes you can't help but think that the cause is bugs in the new system. However, it may not.

Apart from the Sequoia errors, backup disk connection issues, insufficient disk space, Mac sleep mode, and backup disk corruption are also possible causes for a Time Machine backup failure.

So, follow our solutions below based on the error message enlightenment to fix the Time Machine stuck on preparing backup, Mac not recognizing Time Machine backup, Time Machine could not backup the disk because it is nearly full, and Time Machine backup cannot be completed.

Fix 1. Check the connection of the Time Machine backup disk

Time Machine backup fails after upgrading to macOS Sequoia sometimes is due to faulty connections.

If you see the "The backup disk could not be found" error below when starting a backup, check the connection of the backup disk.

Time Machine couldn't complete the backup to "Time Machine". The backup disk could not be found. Make sure the backup disk is connected or select a different backup disk.

Unplug the external drive and then slightly and slowly reconnect it to the USB port on your Mac. If you use a USB hub, connect it to another port. Change the USB cable if the external drive is still not showing up in Time Machine settings.

For a network drive like Synology NAS (Network Attached Storage), try to delete the old backup folder on it,  re-enable its Time Machine support, and re-connect it with your Mac. Here we take Synology NAS as an example.

If Time Machine wireless backup keeps failing since installing Sequoia and you receive the following error message, check your network.

Time Machine could not complete the backup to 'TimeMachine_bck_share'. The network drive was disconnected from the Mac during a backup. Make sure the computer and the backup drive are on the same network and that the backup drive is turned on.

The key point for using NAS as a remote storage destination for Time Machine is a well, stable, and identical network with your Mac. Once the network is stalled, or the backup disk and your Mac are not on the same network, Time Machine backup will fail.

Fix 2. Turn off the Firewall on your Mac

A user from the Apple community feedback that Time Machine wireless backup keeps failing after upgrading to macOS Sequoia due to a bug in the Firewall feature. The Apple support team said that they are working on a fix for the bug in Firewall.

At present, to resolve the Time Machine backup failures on macOS Sequoia, you can temporarily disable the Firewall when using Time Machine to back up your Mac.

After the Time Machine backup is done, manually turn the Firewall back on.

Share this feasible way to help others fix the Time Machine backup not working issue on macOS Sequoia.

Fix 3. Remove and then re-add the backup drive in the Time Machine settings

Time Machine backup failing after upgrading to macOS Sequoia may also result from the temporary system or Time Machine bugs.

You can forget or remove the backup drive in the Time Machine settings and then add it as the backup destination again. Then, go back up your Mac to see if Time Machine works well this time.

Fix 4. Revert to the default SMB settings with Terminal

SMB (Server Message Block) is a network protocol that allows your Mac to access shared folders and files on a remote server or NAS (Network Attached Storage) device. Sometimes, the SMB settings have temporary errors, causing the Time Machine backup to the NAS to be stuck.

Thus, when the Time Machine backup on macOS Sequoia cannot be completed on your network drive,  you can revert the SMB settings to the default.

Now, your Mac will revert to the default SMB settings. Go to check if Time Machine has passed the prior errors and is completing the backup.

Fix 5. Prevent your Mac from automatically sleeping

Time Machine will not back up to your NAS or external hard drive when your Mac sleeps. You can change the settings to block your Mac from automatically going to sleep mode when the display is off.

Fix 6. Free up more storage space on the Time Machine backup disk

Time Machine couldn't complete the backup on macOS Sequoia which may be due to the limited available storage on the external drive or NAS. You may see error hints like the one below.

Time Machine couldn't complete the backup to "My Passport". The backup disk image could not be created.

Time Machine could not complete the backup to "Time Machine Backup". Backup of "Library/Safari/History.db" could not be created.

You can check how much free space your backup disk has and free up more by deleting the old Time Machine backups. If the backup drive has a small capacity, change it to a larger one.

Fix 7. Change another way to back up your Mac

Time Machine failure always happens with every Mac OS upgrade and usually due to the new system bugs. We suggest you back up your Mac with a third-party backup tool like iBoysoft DiskGeeker.

This disk management tool for Mac features with File Keeper and Disk Clone functions. You can use the File Keeper feature to sync your user data volume (the Macintosh HD - Data volume) for data restoration if accidental data deletion occurs in the future.

You can also use the Disk Clone feature to make a one-to-one copy of your entire startup disk to an external hard drive for backup of your Mac.

How to use iBoysoft DiskGeeker to sync data on your user data volume (Macintosh HD - Data)

Step 1. Start backup

Step 2. Search and restore files from File Keeper backups

How to use iBoysoft DiskGeeker to clone your Mac startup disk to an external drive:

Step 1. Preparations

Step 2. Start clone the Mac startup disk

Fix 8. Update your Mac

The last bullet is updating your Mac. If Time Machine backup fails on macOS 15.0.1 yet after trying the above workarounds, you should update your Mac. The Apple support team admits that a bug in Sequoia causes this issue.

If you think the solutions mentioned above are useful, share them to help your friends who also encounter Time Machine backup failing after upgrading to macOS Sequoia.

Why is Time Machine backup failing after updating to macOS Sequoia?

It is not rare that Time Machine backup fails after upgrading to Sequoia. The causes are various, including macOS Sequoia bugs, connection issues with the backup disk, interference from the Mac sleep mode, insufficient backup disk space, backup disk errors, etc. But it turns out that the firewall bugs are the troublemakers because the Time Machine wireless backup keeps failing since installing Sequoia, not the wired backup.

If you think this post is readable for those whose Time Machine backups fail after upgrading to macOS Sequoia, share it with them.