How to resolve error "OneNote can't sync your notes right now. We'll keep trying. (Error code: 0xE0000644 9zu13)"

Craig Arnold 25 Reputation points
2026-09-18T06:32:41.1666667+00:00

I have been a OneNote user for many years, and I have just noticed that one of my folders is not synchronizing and is showing the following error code.

"OneNote can't sync your notes right now. We'll keep trying. (Error code: 0xE0000644 9zu13)"

I've tried to research online how to resolve this, but still, this error prevails, and I remain unable to synchronize my OneNote from my iPad onto the PC and vice versa.

Microsoft 365 and Office | OneNote | For home | iOS
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AI answer

2026-09-18T06:33:02.3733333+00:00

For error 0xE0000644 9zu13, the most relevant fixes are:

  1. Check section and section group names for special characters This error has been associated with section or section group names that contain special characters and block syncing. Rename any affected section or section group to use only letters, numbers, spaces, -, or _. Characters such as +, #, or % have been reported to cause this issue.
  2. Force a sync after renaming In OneNote on the PC, go to File > Info > View Sync Status and select Sync All.
  3. If one section appears to be the trigger, isolate it If the problem happens only in one section or section group, create a new section and test syncing there. If needed, recreate the problematic section in the notebook and test again.
  4. Clear the OneNote cache on Windows This can remove corrupted local cache data.
    • Close OneNote completely.
    • Open %localappdata%\Microsoft\OneNote\16.0
    • Open the cache folder and delete its contents.
    • Reopen OneNote and allow it to rebuild the cache and resync.
    Warning: clearing the cache can remove local-only edits that have not synced yet.
  5. On iPad, force a notebook sync In OneNote for iOS, pull down the Notebooks list. A spinning progress indicator should appear while OneNote attempts to re-sync open notebooks.
  6. Make sure OneNote is up to date on both devices Use the latest version of OneNote for iOS and the latest OneNote version on the PC.
  7. If account authentication is involved, reopen the notebook from the web If the notebook opens correctly in OneNote for the web, close the notebook in the app, open it from OneDrive in the browser, and then select Open In OneNote. If prompted, sign in with the same account associated with the notebook.

If the issue continues after these steps, sign out of all accounts associated with OneNote and sign in again.

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  1. Thomas4-N 22,295 Reputation points Microsoft External Staff Moderator
    2026-09-19T12:37:22.4033333+00:00

    Hello Craig Arnold,

    Sorry you’re dealing with this, especially when the same notebook needs to stay synced between your iPad and PC.

    Before clearing the OneNote cache, signing out, or reinstalling anything, could you check two things?

    1. Open the affected notebook in OneNote for the web and see whether your latest notes appear there.
    2. On the PC, open File > Info > View Sync Status and check whether OneNote identifies a particular section that is failing.

    Please let me know what you find, particularly whether the latest notes are visible online and which section, if any, shows the 0xE0000644 9zu13 error.

    I would avoid signing out or clearing the cache for now if either device contains changes that have not synchronized yet.

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  2. Craig Arnold 25 Reputation points
    2026-09-20T16:37:59.67+00:00

    Thanks for sharing a few solutions for how to resolve the situation.

    I must admit I tried all of the above, as well as simply deleting the new folder, which, by the way, did not have any special characters in its labels or content.

    That seemed to resolve the synchronization challenge, and now the entire workbook is functioning correctly.

    Many thanks for the prompt provision of a resolution and for following up.

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