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How to fix "Sync encountered an error while syncing:Unknown error."

  • 11 replies
  • 13 have this problem
  • Last reply by Andrew

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In mid July, after the firefox update, I had decided to close firefox like I usually do before I open the client for my MMORPG Aion, so I did. I end up not turning on firefox for a few days and when I did my bookmarks were gone as well as my toolbar bookmarks and my history. I start to wonder what happened and then I realised that there was a grey bar at the bottom of my browser stating, "Sync encountered an error while syncing: Unknown error. Sync will automatically retry this action.." I had no idea why this would happen as I never had this problem before so I look at the firefox support database but since I'm quite the greenhorn when it comes to programming there was only so much I could understand. I did try looking for corrupt or locked profiles but I saw none. Now as of today it's going on 2 months since the problem began and just today I recieved the firefox 32.0 update but still have this problem so I'm at my wits end and I not sure if I'll ever get it working again. Also my sync account is the one under the new system I had updated a few days before the problem began it also seems to be working on my other devices. Im lost without my bookmarks please help.

All Replies (11)

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hello Amarynthia, when you type about:sync-log into the address bar and open the latest one or two error logs, can you copy their contents and put them into or a similar service and paste a link here on the forum? this would be very helpful in assessing the problem. thank you!

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Thank you for the help philipp, here are the two most recent logs (most recent is the first one;

Modified by Amarynthia

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It is possible that there is a problem with the places.sqlite database file.

It is best to disconnect temporarily from Sync or at least exclude the bookmarks while trying to fix this.

You can try this extension first.

You can check for problems with the places.sqlite database file in the Firefox profile folder.

If necessary then see if you can restore the bookmarks from an older JSON backup in the bookmarkbackups folder. The xxxx in the name of the backup file denotes the total number of bookmarks including folders and separators in an automatic backup. The trailing $$$$ is a hash to avoid creating the same backup over and over if now changes have occurred.

  • bookmarks-####-##-##_xxxx_$$$$.json
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I get this same error message intermittently. I haven't a clue what to look for at about:sync-log, so have pasted at pastebin.

Thanks for your help.

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hello Andrew, can you try if it's different when you disable your session manager addon or disable tab-sync?

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I'm having this problem too. I don't sync tabs. I use Tab Mix Plus as my session manager. This problem started on 11/6 and hasn't stopped. I've disabled and enabled sync.

Current error report: initial error report on 11/6:

Any help would be appreciated. It's a bit annoying.

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As the problem's intermittent, I've had to wait for it to occur again. Not sure which addon/feature you mean by tab-sync - maybe you'd let us know?

Having had "Sync encountered an error while syncing:Unknown error" again, I disabled my Session Manager addon, restarted Firefox, and opened the same webpage. No error. But would that have been the case anyway (as the problem's intermittent)? Hard to know.

I can't disable Session Manager for any length of time, as I depend on it.

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Hi crogs571

The first sync report shows an error with the history:

1415979204255   Sync.Status        DEBUG   Status for engine history: error.engine.reason.record_upload_fail
1415979204255   Sync.Status        DEBUG   Status.service: success.status_ok => error.sync.failed_partial
1415979204255   Sync.ErrorHandler  DEBUG     history failed: <html>
<head><title>413 Request Entity Too Large</title></head>
<body bgcolor="white">
<center><h1>413 Request Entity Too Large</h1></center>
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Same error msg again.

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Well I deleted cache and something else in the history and hit sync again. So far so good. Thanks for the guidance.

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Still same problem.