Unable to edit my OneNote files

To better understand the situation, could you please confirm whether these are notebooks you created yourself or notebooks shared with you by someone else? Also, does the error affect every notebook or only certain ones? Have you recently changed your Microsoft account password or started using OneNote on a different device?

Please try to sign in to https://www.onenote.com using the same Microsoft account associated with your notebooks and check whether you can open and edit them directly in your browser.

If the notebooks work online but not in the desktop application, this may indicate a local authentication or synchronization issue. If the same permission error appears online, open https://onedrive.live.com and verify that the notebooks are accessible under the correct account.

For shared notebooks, the owner may need to verify that you have editing permissions. Microsoft's official troubleshooting instructions are available here:

https://support.microsoft.com/onenote/onenote-help-and-learning/fix-issues-when-you-can-t-sync-onenote.

Please let me know whether the notebooks work in the browser to determine the appropriate next step without risking any unsynchronized notes.