OneNote can't sync one of my notebooks - code 9zu13

Question

OneNote can't sync one of my notebooks - code 9zu13

Micah Smith 25

I am getting the following error message when trying to sync of one my Notebooks:

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

All other notebooks are fine, and update no problem.

I've tried restarting the app, and restarting the computer.

I have tried removing the cache (save it as a different folder name).

I have tried looking for extra accounts and removing those.

I signed out of my account. Then logged back in. And tried to open only the problem notebook. It would sync updates to much of the notebook.

If I add a new section, to one specific section group, then I get the error again. I can update pages, and section titles that already exist in that section group, but I can't add a section to that one specific group without the error happening. If I delete the page, it syncs without error.

Tomas Hrda 10 Reputation points

2026-06-15T15:03:16.4366667+00:00
Today, OneNote really "pleased" me again. I opened my primary notebook, but suddenly it couldn't be edited, and I got this notification:

"This notebook is in read-only mode because it is broken. A backup has been created. To continue editing, please copy the content into a new notebook and close this one."

Well, great! As always, OneNote "didn't disappoint"!

So, I created a new notebook. I hadn't even written anything in it yet, didn't copy anything, didn't rename anything, and didn't even create a page, and this brand-new notebook was already showing a sync error "0xe402007f" - a completely new, empty notebook!!! :D

I tried again, this time creating it on the OneDrive cloud. I opened the notebook in the desktop app and started copying the content from the broken notebook to the new one.

You can't copy in bulk; you have to do it section by section, and if you have a section group, you can't copy that at all. You have to manually copy all the sections contained within the group one by one. If you have dozens of sections, expect it to take dozens of minutes. And the outcome is uncertain anyway!!! It might happen to you, just like it did to me, that copying a section stops responding. The result? The new notebook is broken, won't sync, and shows the error "OneNote can't sync your notes right now. We'll keep trying. (Error code: 0xE0000644 9zu13)". None of the sections or groups have any special characters in their names. So I have to start over!!!

The result?

The original notebook is broken, and copying its content to another one is incredibly slow.

One new, empty, local notebook that couldn't sync the moment I created it. It can't be deleted, only closed, so its name will haunt my notebook list forever.

A second new notebook, into which I only managed to copy a portion of the data before it also broke.

Roughly 2 hours of wasted time.

Over the years of using OneNote, I've had dozens of similarly broken notebooks - inconsistent data and notes, broken and unfinished syncs, missing notes...

ONE NOTE IS A DISASTER.

Answer recommended by moderator

Micah Smith 25

Removed special characters from section group, and section names. For me, it was a "+" sign.

When I removed that from the section group name, any new sections added nested under that section group were no longer a problem with the synchronization.

Micah Smith 25 Reputation points

2026-02-10T21:54:14.25+00:00

I'm not sure how to accept this answer as the answer.
Norah-L 9,655 Reputation points Microsoft External Staff Moderator

2026-02-11T00:50:03.3066667+00:00

Micah, I’ve marked it for you already. Thanks for sharing, this will be helpful for others too!
Francisco Mota 0 Reputation points

2026-02-21T09:44:35.9+00:00

This also helped resolve my issue.

I had one section group with commas, so I replaced the commas with dashes.

Another section group had a '+' character for which I removed altogether.

I shouldn't be allowed to use special characters in section groups to begin with.

2 additional answers

Your answer

Micah Smith 25 Reputation points

2026-02-10T21:54:14.25+00:00

I'm not sure how to accept this answer as the answer.
Norah-L 9,655 Reputation points Microsoft External Staff Moderator

2026-02-11T00:50:03.3066667+00:00

Micah, I’ve marked it for you already. Thanks for sharing, this will be helpful for others too!
Francisco Mota 0 Reputation points

2026-02-21T09:44:35.9+00:00

This also helped resolve my issue.

I had one section group with commas, so I replaced the commas with dashes.

Another section group had a '+' character for which I removed altogether.

I shouldn't be allowed to use special characters in section groups to begin with.

Answer 1

I have the same issue on two netbooks which never caused any problems before. I don’t have any special characters in the names of sections, sections groups, or the notebook itself.

I strongly recommend that everyone avoid using the OneNote app at all costs. Unfortunately, I’ve been trying to use OneNote for years now and I have a lot of data stored in several notebooks—what a terrible mistake that was. In those roughly 10 years, many notebooks broke, their synchronization failed, or they got corrupted for some reason. I used it on two computers and one mobile phone. For some notebooks I have dozens of copies in various states because their sync, move, or rename failed. I’d rather not even talk about the huge amount of lost data and broken sections. And even when it occasionally works, on a super‑fast computer with an Intel Core 9 and 64 GB RAM the app often lags so badly that you can’t even type plain text. The mobile app is practically unusable.

Stay away from the tragedy called Microsoft OneNote—or you will regret it one day!!!

Answer 2

Norah-L 9,655 Microsoft External Staff Moderator

Hello Micah Smith!

Thanks for posting your question to the Q&A forum.

I understand you're experiencing a syncing issue with one of your OneNote notebooks, receiving the error message: OneNote can't sync your notes right now. We'll keep trying. (Error code: 0xE0000644 9zu13). while other notebooks are syncing without issue. Here are a few additional steps you can try:

1. Check OneNote for updates

Make sure you are using the latest version of OneNote. Go to the Microsoft Store (for Universal Windows Platform version) or the Microsoft website (for desktop) to check for any available updates.

2. Reset OneNote

If the issue persists, you could perform a reset by deleting the local cache folder

Press Windows + R, type %localappdata%\Microsoft\OneNote\ and delete the folder for the version you're using (e.g., 16.0 for Office 2016).

3. Create a new clean group section (workaround)

Copy (not move) all pages into the new section
Sync with Shift + F9
If it syncs, delete the old corrupted section, then rename the new one.

If the issue continues, please try more troubleshooting methods given in this official Microsoft article: Fix issues when you can’t sync OneNote

I look forward to hearing how it goes!

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Norah-L 9,655 Reputation points Microsoft External Staff Moderator

2026-02-09T08:01:07.9433333+00:00

Hi Micah Smith!

May I know whether your issue has been solved or not?

If not, please share your updates here. We can work together to figure it out.
Micah Smith 25 Reputation points

2026-02-10T21:51:24.6133333+00:00

Hi, thanks for checking back in with me. I looked for updates, I did the reset.

Those didn't work for my error: (Error code: 0xE0000644 9zu13)

I decided to try recreating the problematic section group. I discovered what I think is the problem.

When I had a special character in the section group title, "+" was the one in question, it would not update. So, I removed that, and then any section addition after that, worked ok.

There was a nested section group as well, that had a special character in it. When I double clicked the name of these ones with a special character, it was transformed from "+" into ^J and ^M for the other one, I think. I might be off on what it was actually transformed into. Oddly, if I test now with renaming a section or section group using "+" it doesn't transform it into a ^ character.

I removed those special characters, and it has sync'd fine.

".", and "-", and "_" all still work in section names. But + seemed to mess things up and the other one I can't recall what it was.
Norah-L 9,655 Reputation points Microsoft External Staff Moderator

2026-02-11T00:34:00.6033333+00:00

Thank you so much for your detailed update, Micah Smith!

I’m glad you found the cause and managed to get it working after all that effort. Your confirmation is really helpful as it could guide others facing the same issue toward a solution.

Wish you a wonderful day!

Warm regards.