While signed in to your Microsoft account, OneNote continually keeps all of your notes in sync. Whenever you work in shared notebooks, OneNote manages your own changes with that of any other authors editing the notebook to make sure that everyone’s work is saved automatically and reliably.
To view the sync status of any of your open notebooks, do the following:
To the left of the section tabs, click the name of the current notebook to open the Notebooks list.
In the list of open notebooks, move the mouse pointer over the name of the notebook you want to check, and then click the button that appears next to it.
Next to Last Sync, verify the date or time the notebook was last synced.