OneNote sync problem with error code : E0000644 9zu13 running MacOS

Question

My Onenote does not sync (only Saved offline) with error code E0000644 9zu13 on my MacBook Air running Sequoia 15.7.4. and my Onenote version is Version 16.107 (26030819) i.e. most updated version.

I'll appreciate any help on this!

Many thanks!

Answer 1

Hello Kevin Fong,

This error E0000644 9zu13 is a OneNote sync issue. It’s usually related to notebook naming, sync cache, or a single notebook getting stuck. I suggest you try this:

1. Check if the issue is the notebook or the Mac app

Go to: https://www.microsoft.com/microsoft-365/onedrive/online-cloud-storage

Sign in with the same account 

Open your notebook in OneNote for the web

Result:

If everything looks correct > issue is with the Mac app

If it doesn’t open or is missing content > issue is with the notebook itself

2. Remove special characters (very common fix)

This specific error is often caused by section/section group names.

Look for names with symbols like: +, #, %, etc.

Rename them using only:

letters (A–Z)

numbers (0–9) 

simple spaces or - _ 

Then try syncing again.

3. Force sync manually

Open OneNote

Right-click (Control + click) the notebook

Select “Sync This Notebook”

4. Reset the notebook connection

Before doing this, copy any important unsynced notes somewhere safe.

Close the notebook in OneNote

Reopen it from OneDrive (File > Open)

5. If only one notebook is affected (workaround)

This usually means the notebook is slightly corrupted.

Create a new notebook

Copy pages/sections into the new one (don’t move)

Sync the new notebook

Important notes:

• Don’t move or sync notebooks using Finder or OneDrive folder copy
• Always open and manage notebooks inside OneNote or OneDrive web
• For more information: https://support.microsoft.com/en-us/office/fix-issues-when-you-can-t-sync-onenote-299495ef-66d1-448f-90c1-b785a6968d45

 I hope this will help with your situation. Please feel free to reach back if you have further update or more questions.

Best Regards,

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Answer 2

Error code 0xE0000644 9zu13 in OneNote for Mac has been observed when section group or section names contain special characters that interfere with sync.

To resolve this, follow these steps on the problematic notebook:

1. Identify the specific section group where adding or syncing sections fails.
2. Rename that section group to remove any special characters (for example, remove characters like "+", symbols, or other non-alphanumeric characters). Use only letters, numbers, spaces, hyphens, or underscores.
3. Also rename any sections under that section group that contain special characters.
4. After renaming, force a sync of the notebook:
   • On macOS, Control-click the notebook name in OneNote and choose the option to sync the notebook.
5. Verify that new sections can now be added and that the notebook syncs without the 0xE0000644 9zu13 error.

If sync issues persist beyond this specific error, also check the general OneNote sync guidance for Mac, including opening the notebook in OneNote for the web and closing/reopening it in OneNote for Mac, and verifying account authentication and updates.

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References:

• OneNote can't sync one of my notebooks - code 9zu13 - Microsoft Q&A
• Fix issues when you can't sync OneNote