A family of Microsoft products that enable users to capture, organize, and reuse notes electronically.
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Hi, Blair
Sorry for this frustration. Seeing your notebook in OneDrive is encouraging, but a 404 can mean the notebook’s location or link has changed; the macOS update alone doesn’t establish the cause.
Here are some suggestions you can try:
Protect any notes still visible on your Mac first. If OneNote still displays pages from the notebook, copy important text into another document before clearing app data or reinstalling anything. In OneNote for Mac, also check File > Open Backups for a saved copy of its sections.
In OneDrive on the web, check Recycle bin for the notebook or any missing folder and restore it if found. If this is a work or school account and it isn’t there, ask your IT administrator to check the second-stage recycle bin and the notebook’s location.
If the notebook is still listed but won’t open, ask the owner or IT administrator to check whether it was moved, renamed, or deleted. Share the exact 404 message with them.