One note is not synchronize with the error code

Dear Alex.

Thank you for your comment and questions.

I reply to yours.

Are you able to see your notes when you sign in to OneNote for the web?
Yes I am.

Is the notebook stored in OneDrive or in a SharePoint / Teams site?

I dont understand perfectly. As long as I can say is I use teams App and sharepoint of Teams. Im not sure my notebook stored in there surely.

Are you signed in to OneNote with a work/school account or a personal Microsoft account?

My accounts is issued by Company. so Yes.

Does the issue affect all notebooks, or only one specific notebook?

To only mine.

Have you recently changed your password or signed in on a new device?

No I have not.

Are you able to create a new notebook, and does the new notebook sync correctly?

of my account, I can`t do that via app. plus any notebook is not on the app.

I tried all of your suggestion, unfortunately no one works out...

In the meantime, please try the steps below in order:

1/ Check your notes in OneNote for the web

If your notes appear there, this confirms your data is safe.

2/ Force a manual sync

Open OneNote on your computer.

Go to File > View Sync Status.

Select Sync Now or Sync All.

3/ Sign out and sign back in

In OneNote, click your profile picture.

Sign out, close OneNote completely, then reopen it and sign in again.

Please understand that our initial response does not always resolve the issue immediately. However, with your help and more detailed information, we can work together to find a solution.

I truly appreciate your patience and understanding. If you have any further questions or need further clarification, please feel free to reach out. I'm looking forward to hearing from you. 

Thank you for your cooperation.

Dear @KIM, TAEHOON,

Thank you for the details.

Since you can see your notes in OneNote for the web, your data is safe. The issue is only with the OneNote desktop app, which is failing to sync and shows error 0xE00009C8.

This usually happens when the desktop app loses its connection to the notebook stored in Teams/SharePoint.

Please try the following:

Close OneNote completely

Open your notebook in OneNote for the web

Select Open in Desktop App to reconnect it

If it still does not sync: please repair or reinstall OneNote, then sign in again with your work account

1/ Repair OneNote

Close OneNote > Open Windows Settings > Apps > Installed apps >Find Microsoft OneNote (or Microsoft 365 Apps) > Select Modify > Repair > Wait for the repair to finish > Open OneNote > Sign in with your work account > Open the notebook and check sync

2/ Reinstall OneNote (If repair does not work)

To uninstall: Close OneNote > Open Windows Settings > Apps > Installed apps > Find Microsoft OneNote (or Microsoft 365 Apps) > Select Uninstall > Restart the computer

To reinstall: Install OneNote (or Microsoft 365 Apps) again (from Microsoft Store or Microsoft 365 portal)

Open OneNote > Sign in with your work account > Open the notebook from OneNote for the web > Select Open in Desktop App

Important Note for the Customer

Your notes are safe because they appear in OneNote for the web

This process only fixes the desktop app connection