OneNote Gem Add-Ins

Missing the File Tab on OneNote Ribbon?

I no longer have a "File" tab in OneNote. Where did it go? All I have is Home / Insert / Draw / Review tabs.
The File tab is only available in the OneNote 2010, 2013, 2016 ribbon in Windows Office.
The OneNote for Windows 10 (UWP) version does not have a File tab.
You can distinguish between OneNote 2016 and OneNote UWP by seeing if the ribbon has the File tab.