A family of Microsoft products that enable users to capture, organize, and reuse notes electronically.
Hello,
This is usually a sync or account issue. Sign out of OneNote on your Mac, then sign back in with the same Microsoft account used on your phone. Open your notebooks again from File, Open Notebook to refresh the connection. Check sync by right clicking the notebook and selecting Sync This Notebook, then keep the app open with a stable internet connection until sync completes. Also check OneNote on the web, if notes appear there, your data is safe and the Mac app needs to resync. If notes do not appear on the web, the notebook may not have been fully synced before.