If you’re seeing the 0xE40105F9 error code, OneNote can’t sync one or more notebooks because you’re using an older version of OneNote that’s no longer supported by the server. To continue syncing your notes, download the latest updates for OneNote, and then try again. Follow the below article for the detailed guide to Fix 0xE40105F9 (Unsupported Client Build) error in OneNote.
Software updates are important because they often include critical patches to security holes. They can also improve the stability of your software, and remove outdated features. All of these updates are aimed at making the user experience better.

Preventions to OneNote Error
- Get the latest version of OneNote for Microsoft Accounts.
- Sign in to the right OneNote Account.
- Set up OneNote to automatically sync notes.
Fix 0xE40105F9 (Unsupported Client Build) error in OneNote
Desktop
- Exit OneNote.
- Go to Control Panel
- System & Security then go to Windows Update.
- Click Check for Updates.
- Select and install all available updates that appear under Microsoft Office.
- If necessary, restart your computer after all of the updates have been applied.
- Start OneNote and then sync your notebooks manually by pressing Shift+F9.
If you don’t have Windows Update configured to include updates for Microsoft Office, you can manually check for OneNote updates by doing the following: