Error code: 0xE0000644 9zu13

Question

I'm getting this error on two notebooks.

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

The latest sync date is 6/18/26 on one notebook and 6/29/26 on the other.

How can I resolve it?

Answer 1

Hi Oileen, 

Thank you for reaching out and for providing the error code and sync dates. Based on the details you shared, the error code 0xE0000644 (9zu13) usually appears when a section or section group name contains a special character that blocks syncing, or when the local OneNote cache is corrupted. Please work through the steps below in order. 

1. Force OneNote to sync 

• In OneNote, go to File > Info > View Sync Status. 

 

• Select Sync All.  

 

• This confirms whether the error clears on its own before you make any further changes. 

2. Remove special characters from section and section group names 

In each affected notebook, rename any section group or section that contains symbols such as +, #, %, or similar. Use only letters, numbers, spaces, or - and _.  

For example, change Projects + Ideas to Projects and Ideas, then trigger a manual sync. 

3. Clear the OneNote cache.  

• Close OneNote completely. 
• Press Windows + R, type %localappdata%\Microsoft\OneNote\16.0, and press Enter. 
• Open the cache folder and delete its contents. 
• Reopen OneNote. It will rebuild the cache and re-sync your notebooks from the cloud. 

4. Repair Office.  

• Close all Office applications (Word, PowerPoint, Excel, Outlook, etc.).       
• Open Windows Settings (press Windows + I).       
• Go to Apps > Installed apps.       

    

• Find Microsoft 365 / Microsoft Office in the list.      
• Select the three dots (…) next to it and choose Modify.       

  

• If prompted by User Account Control, select Yes.      
• Choose Online Repair > then select Repair.      

• Follow the on‑screen instructions until it completes.      

I hope this information is helpful. Please follow the steps above and let me know if it works for you. If not, we can continue working together to resolve the issue.  

If you found the response useful, please consider marking it as accepted, as this may help other community members who are looking for similar guidance.  

Thank you for your patience and understanding. I look forward to continuing the conversation. 

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