"To sync this notebook, sign in to OneNote."

When I open one particular notebook in OneNote 2016, OneNote displays the message:

"To sync this notebook, sign in to OneNote"

and the Shared Notebook Synchronization window shows this error:

"We need the password to sync this notebook. (Error code: 0x803D0005) There was an error communicating with the endpoint at [my OneDrive]; The server returned HTTP status code '401 (0x191)' with text 'Unauthorized'.; The requested resource requires user authentication.; The operation identifier is not valid."

Error code 0x803D0005 means that OneNote is unable to communicate with the OneDrive server where my notebooks are stored, and the reason is HTTP status code 401, which means that OneNote's request to my OneDrive lacks valid authentication credentials - my password. The error message does not reference any Section in particular.

According to File > Account > User Information in OneNote 2016, I am in fact signed in to my Microsoft account. Nevertheless, if I open the affected notebook in OneNote for the web (with the notebook's URL) I can see that recent changes have not synced.

Manually syncing my notebook solves the problem (and I'm not asked to enter my password.) I want to know why this one notebook won't sync automatically - why I must sync it manually?

It's not an issue with OneDrive, since according to Microsoft's Service Status web page OneDrive is up and running.

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To anyone who likes to answer by copying URLs for me to read: I have already read and performed the steps in Troubleshoot synchronization errors in OneNote 2016 for Windows and Fix issues when you can't sync OneNote. In addition, please know that my OneNote notebooks are not stored on Sharepoint and no one else collaborates on any of my Notebooks. Also, please know that I have already uninstalled and re-installed OneNote 2016.