You should see the option to update OneNote there. If you've downloaded OneNote from the Mac App Store, launch the App Store and check for Updates. Please update to the latest version of OneNote for Mac, iPhone and iPad. Similarly, OneNote may require you to sign in repeatedly to resolve sync errors. If you use OneNote 2016 for Mac and OneNote for iPhone and iPad, you may be asked to sign in any time you open the OneNote app or when you switch between notebooks.
