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.
If you temporarily disconnect from the Internet for any reason (for example, while traveling on an airplane), you can keep working offline in the cached (locally saved) copy of the notes on your Mac. While you work offline, OneNote will warn you that it cannot sync the notebook. As soon as you reconnect to the Internet, OneNote will automatically sync your changes to the notebook on OneDrive. After syncing shared notebooks, you’ll be able to see any notes from the other notebook authors that were added or changed during the time you were offline — and they will be able to see the changes you have made.
Note: Whenever you’re working offline, your notebooks will show an offline icon next to your notebook name.
Tip: To check the last time your notebook was synced, open the Notebooks list, move the mouse pointer over the name of the notebook you want to check, and then click the button that appears next to it. To manually sync your notebook click Sync.