Time Machine on Mac won't back up!

This is going to sound crazy, but do you have the FindMy widget running? I had this problem begin around the time I upgraded to macOS 15.2 and it was driving me crazy. The failure didn't occur unless the screen was locked, but it was inevitable if the screen was locked. I had tried to internet search my way to a solution a few times. I finally found it in this recent (Nov. 2024) post on MacRumors (https://forums.macrumors.com/threads/time-machine-error.2437741/ ) where the user checked the logs and discovers it is FindMy.

Assuming it is shortly after you have received this error message

Time Machine did not finish backing up because some files were unavailable. Backups will resume when your Mac is unlocked.

This is how you can check if FindMy is suspect on your machine:

1. Open the Terminal (in the Finder, go to Go > Utilities and then open Terminal or just Spotlight this)
2. Enter the following command exactly:

log show --info --style compact --predicate '(subsystem == "com.apple.TimeMachine")' --last 24h | grep "Operation not permitted"

This command searches the logs for the last 24 hours and sees if anything associated with TimeMachine triggered an "Operation not permitted" error. Lo and behold I had several lines of the same error (other than date stamps)

2025-01-25 12:38:29.847 E backupd[586:423f16d] [com.apple.TimeMachine:FileProtection] Failed to acquire device lock assertion for '/Volumes/com.apple.TimeMachine.localsnapshots/Backups.backupdb/DRIVENAME/2025-01-25-121611/Data/Users/USERNAME/Library/Containers/com.apple.findmy.FindMyWidgetItems/Data/SystemData/com.apple.chrono/snapshots/com.apple.findmy.FindMyWidgetItems/systemSmall--4438004920846669853----164.00w--164.00h--20.00r--0f--0.00t-0.00l-0.00b0.00t.chrono-timeline' (assertion state: <dropped>), error: Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"

So it appears the FindMy widget creates some sort of temporary files that TimeMachine is not being allowed access to, causing the failure. I had to turn off the FindMy widget and reboot (just turning off the widget didn't appear to release the file lock)... but my Time Machine is now working fine with the screen locked!

Maybe other apps can cause these problems, so this command might at least give us an idea of which file is causing the "Operation not permitted" with Time Machine.

GeneLand wrote:

This is an update on a previous thread I started about Time Machine not able to finish a backup on a M1 MacBook Pro. That problem was resolved with help from Apple Support instructions and entering some commands in Terminal.

It actually wasn't, and that problem appeared to have been complicated by the presence of some non-Apple "anti-virus" junk. If you have not yet removed whatever that may have been — uninstalled it completely — then you will continue to have problems with Time Machine as well as many other fundamental aspects of using a Mac.

So be sure to do that forthwith.

HWTech wrote:

This appears to be the older thread (now locked):

Time Machine on Mac won't back up! - Apple Community

In that older Discussion the Apple Support representative came close to providing a solution, but the particular solution he or she suggested would have had no effect. A better idea would have been to "reconnect" to Time Machine, a procedure which I'll describe below for future reference. Try it. It may or may not help, but it's harmless in that it will not affect your existing backups at all.

The following technique can be used to "reconnect" to the backup disk. It will not affect the existing backup history in any way.

Open Time Machine's Preferences and de-select the Back Up Automatically checkbox. Make sure no backups are in progress, otherwise you should wait for it to finish or terminate.

• If the backup disk is directly connected to the Mac, disconnect it: drag its icon to the Trash, wait for it to disappear from the Desktop, and then physically disconnect it from the Mac.
• If its icon does not appear on the Desktop, select External Disks in the Finder menu > Preferences... > General. You can de-select it later.

Then, click the "Select Disk..." button, select the backup disk, then Remove Disk, then Stop Using This Disk.

• If you designated more than one backup destination, the "Select Disk..." button is replaced by an "Add or Remove Backup Disk..." option. You may have to scroll through the list of backup disks for that option to become visible.

This will not affect any existing backups.

• If the backup disk had been directly connected to your Mac, reconnect the backup disk, power it on if required, and wait for its icon to appear on the Desktop.

Then, Select Disk... again in Time Machine's Preferences. Re-select the same one under Available Disks, then Use Disk.

• If the backup is on a network (TC or AEBS), you will be prompted for the password you provided for that disk in AirPort Utility.
• If the backup was encrypted, you will also be asked for the backup encryption password.

"Waiting to complete first backup" will appear, which means it won't do anything until the next scheduled backup. Despite the implication of that message, it does not mean it needs to create a completely new backup, as if it's creating a brand new one. Your existing backups will still be available.

• If you don't want to wait that long, select Back Up Now.

A Notification may appear if your source volume is encrypted and the backup volume is not. That's normal.

Re-select Back Up Automatically. The "Preparing Backup..." status message will remain for a long time. Eventually, "Backing up xxx of yyy" will appear, but those values will not be accurate, nor will the "Estimated time remaining" in Time Machine's Preferences. Just ignore it. It may take a few hours even if your Mac is not allowed to sleep. Time Machine will also pause or become slow if you use your Mac for tasks it considers a higher priority.

Hey again!

I did post another discussion earlier that may have the steps to resolve your backup problem.

Likewise sometimes deleting any failed backups resolved this issue:

In Finder open the backup drive > backups folder, and delete any file that says “in progress” as long as it’s not currently backing up, then try again.

Here is another good resource as well if needed:

Time Machine troubleshooting on Mac - Apple Support

Likewise while it’s backing up you can run “tmutil status” in Terminal for more info about what it’s currently doing.

The Console app may also give clues to what’s happening and why it’s failing to backup. I believe “backupd” is the process.

I’m also wondering if some of your data in any cloud service is causing a problem hence the error that files couldn’t be found, perhaps excluding some folders in the Time Machine settings and trying again may help you to narrow it down to a particular folder causing the problem.

And if able to test, is there another external drive you can try backing up to, just to rule out that this external drive is having issues?

Hope something here helps!

Next step, download and run EtreCheck.

Instructions: How to use the Add Text Feature When Posting Large Amounts of Text, i.e. an Etrecheck Report - Apple Community

It may or may not reveal anything of interest, but it will provide more information than we have now.

Yeah, the bug with the screen lock is a problem. It surfaced with the original release of Sequoia and persists for many to this day. Unsure if Apple will ever address.

Per other recommendations, I've added Time Machine.app and TMHelperAgent.app to the "Allow Incoming Connections" within the Firewall setting, but this doesn't help.

If the screen is unlocked, Time Machine runs without issue.

Fix this Apple!

If you can't back up or restore your Mac using Time Machine

If you can't back up or restore your Mac using Time Machine - Apple Support (CA)

The user in this post may hold a solution:

What causes Time Machine to stall during … - Apple Community

Hope that’s the case! If not I can think of a few things to check out!

If I let my mac go to screen lock and a time machine backup occurs I get the following:

if I unlock my screen and prevent it from locking backups work fine.

Any idea how to fix this so I may lock my screen?

You really should provide the link to the other thread for reference purposes. This appears to be the older thread (now locked):

Time Machine on Mac won't back up! - Apple Community

Did you try the same fix with this other Mac?

It appears that Siri AI is the sole developer of new versions of macOS.

15.2 breaks Time Machine backups on Apple Silicon Macs

Just chill and wait for a fix, or try to downgrade your Mac