Sync session failed to start

Question

Sync session failed to start

I give up, I cannot figure out why I cannot sync my iPhone and iPad with my Mac running Big Sur. I get the following message below. Nothing pops out when looking at logs in Console

The iPhone “David’ Ms iPhone” could not be synced because the sync session failed to start.

Can anyone help get my sync working in Big Sur?

I see the following in the system.log file

***

Jun 19 07:33:15 Davids-iMac syncdefaultsd[57895]: objc[57895]: Class SYDClient is implemented in both /System/Library/PrivateFrameworks/SyncedDefaults.framework/Versions/A/SyncedDefaults and /System/Library/PrivateFrameworks/SyncedDefaults.framework/Support/syncdefaultsd. One of the two will be used. Which one is undefined.

Jun 19 07:33:15 Davids-iMac syncdefaultsd[57895]: objc[57895]: Class SYDJournal is implemented in both /System/Library/PrivateFrameworks/SyncedDefaults.framework/Versions/A/SyncedDefaults and /System/Library/PrivateFrameworks/SyncedDefaults.framework/Support/syncdefaultsd. One of the two will be used. Which one is undefined.

Jun 19 07:34:30 Davids-iMac com.apple.xpc.launchd[1] (com.apple.mdworker.shared.0C000000-0300-0000-0000-000000000000[57882]): Service exited due to SIGKILL | sent by mds[84]

***

The file /System/Library/PrivateFrameworks/SyncedDefaults.framework/Versions/A/SyncedDefaults does not exist

The file /System/Library/PrivateFrameworks/SyncedDefaults.framework/Support/syncdefaultsd appears to be an binary executable file

iMac Line (2012 and Later)

Posted on Jun 19, 2021 5:02 AM

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Answer 1

Jun 26, 2021 7:26 AM in response to AnnieL2

Thanks for the help. My Mac now syncs with both my iPhone and iPad.

You steered me to the sync setting on Mac. Things started working after I turned off syncing Audiobooks. I'm not sure if there is a problem with Audiobooks or if the change rebuilt a sync settings/preferences file. My guess is Audiobooks because I get warnings when I reenabled syncing. Therefore, no audiobook syncing through Finder setting in the future.

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Answer 2

AnnieL2

Community Specialist

Jun 20, 2021 9:27 AM in response to David Morsberger

Hello David Morsberger,

From your post we see that you’re encountering an error that the sync session is failing to start when syncing your devices with your Mac.

Let’s start isolating. What type of data are you syncing? Does it happen with multiple types? If you’re attempting to sync more than one type of data at a time, does it persist if we pull things back to one type of data?

Another thing we can test is checking the situation in safe mode. Though safe mode does make it so some that connect via USB might not work. Just let us know if your iPad and iPhone aren’t seen at all in this mode. How to use safe mode on your Mac

Thanks.

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Answer 3

AnnieL2

Community Specialist

Jun 21, 2021 8:59 AM in response to David Morsberger

David,

We understand needing some time to get to safe mode. Let us know how it goes.

As far as other data syncing, we're asking if you're syncing music and videos and photos all at the same time. Just to try and isolate if the media being synced might be involved.

Thanks.

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Answer 4

AnnieL2

Community Specialist

Jun 27, 2021 1:23 PM in response to David Morsberger

David,

We're glad you were able to sync the majority of your data. If you wanted to drill down farther, you could try syncing one audiobook at a time or 1/2 of your audiobooks, then if still an issue, cut that half in half in the process of finding where the culprit is.

Let us know if you have any questions.

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Answer 5

Jun 21, 2021 5:04 AM in response to AnnieL2

Thanks!

This is only occurring when syncing my iPhone and iPad. Fails when pressing Sync button in Finder winder when connected via wifi or USB.

I'm not sure what other types of data is synced.

I will try safe mode later. I have critical things running on my iMac.

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Sync session failed to start

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