OneNote missing files

Because the content is also absent in OneNote for the web, this is not evidence of desktop-cache damage. OneDrive’s confirmation that notebook files exist does not, by itself, prove every section and page remains readable.
Before resetting, reinstalling, signing out, or closing notebooks, preserve any locally available unsynchronized notes and backups. Those actions can remove local cached content that has not reached the service.
Open the affected notebook directly from its OneDrive location, confirm the account and notebook identity, and record whether sections, pages, or only their contents are missing. Check OneNote’s notebook recycle bin and available backups without overwriting the current notebook.
Return the case to OneNote support with the OneDrive findings, notebook identifiers, affected section examples, app version, timestamps, and any sync error codes. Ask for investigation of the reproducible web-side problem rather than another desktop-only reset. Public responders cannot reconstruct or guarantee recovery of unavailable notebook content