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How to fix the Firefox Sync Unkown Error in 3 Steps

Posted in Computers, Internet and World Wide Web, Software on July 6, 2017
Tags: , , , , , ,

Recently I've been getting an annoying error from Firefox 5.0 at the bottom of the browser saying: Sync encountered an error while syncing: Unknown error. Sync will automatically retry this action.

Solution to Firefox Sync Error Unknown

Don't delete anything yet! Many people say you need to delete your FireFox Sync account and even reinstall the browser. But here's the easier the solution that worked for me without the need for any re-installation and it's all done online. Login, Clear your Sync data, Sync! You don't even have to close your browser.

The "Before you do anything" solution:

Login to your Sync account online. After the log in, restart your Firefox browser. See if that did the trick. If that doesn't work. Continue to this next part...

Solution #1 (in case that didn't work - THIS solution worked for me)

  1. Login to your online Firefox sync account here https://account.services.mozilla.com/
  2. Click Clear your Sync data and then click the button. Once you've done this you'll get the confirmation message "Your data has been successfully removed from your sync cluster".
  3. Now click the Sync button if the error bar is still showing in Firefox. If not, click on the orange Firefox drop-down and click Sync Now. If you're using the Menu Bar, you can click on Tools then click Sync Now. (Don't  know what I'm talking about? Click here to see the image if you're new to FireFox.)

If that didn't work, here are some more solutions you can try.

Solution #2 (in case that didn't work)

For for this solution I'm using the regular menu, not the orange menu button. If you only see the orange button you can hit the "Alt" button on your keyboard and the old style menu will appear. If you don't know what I'm talking about, see a screenshot here.

  1. Backup your bookmarks to prevent any possible loss. Go the Firefox menu and click Bookmarks > Show All Bookmarks > then click Import and Backup > Backup.
  2. Go to the sync tab in your firefox preferences. In the menu click Tools > Options > Sync. Uncheck everything except passwords and close.
  3. Now sync your data. Click Tools > Sync Now.
  4. Go back to the sync tab in your preferences and enable each box one by one (for whatever you want to sync) and do a sync in between.
  5. Restart your browser, see if that solves the problem!

Solution #3 (in case that didn't work)

Contact Firefox support. You can do a live chat with them here. They might send you to this page "Firefox Sync is not working" but it didn't solve my problem. Good luck!

Click this if you forgot your Firefox Sync key and want to know how to regenerate one. Click this to learn how to setup a new Firefox Sync account.

3 Responses to “How to fix the Firefox Sync Unkown Error in 3 Steps”

  1. lliseil says:

    Thank you for the tips.
    Even if they didn't solve my issue, helped me to further narrow its cause then resolve it.
    Having a look at Sync's logs (type 'about:sync-log' into the Address bar) is of a great help, especially if going to the Mozillal Support forums (rather nice btw).
    Cheers!

    ps : the issue preventing Sync to work in this location was caused by a wrong permission on the folder 'Bookmarksbackup'.
    Appeared like this in Sync's logs :
    ---
    Sync.Status DEBUG Status.service: success.status_ok => error.sync.failed_partial
    Sync.ErrorHandler DEBUG bookmarks failed: Component returned failure code: 0x80520015 (NS_ERROR_FILE_ACCESS_DENIED) [nsIFile.create]
    ---
    'NS_ERROR_FILE_ACCESS_DENIED' being the key here.

  2. Sylvia says:

    It works! This was driving me nuts. Thanks so much! 🙂

    • I'm glad it worked for you and thanks for leaving a comment. I searched a few times and the only solution I could find was to delete and reinstall. I was lazy, didn't want to do it, and a week later I found this solution that worked out a lot better for me.

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