Windows Wrinkles Ironed out. 

Wrinkle No 2a: The Case of the Missing Office Ribbon Toolbars

Where have all the ribbons gone?
From my software interface.
Where have all the ribbons gone?
Not so long ago.
Where have all the ribbons gone?
Buried by updates every one.
But here's some keyboard hacks to bring them back
Here's some hacks to bring them back

— With apologies to Mr. Pete Seeger

You may have noticed the Ribbon Toolbars have disappeared lately from your Office applications.  I am not sure when Ribbon got turned off by default, but now the Ribbons are apparently turned off by default.  And the button toggle that toggled the Ribbons on and off has been replaced with a Diamond Icon. Click the Diamond to learn about your "Benefits." 

There has always been a keyboard shortcut to toggle the Ribbons on and off, it's just that until now you did not need to know the shortcut.
The keyboard shortcut to toggle the Ribbons on and off is Control Key + F1. 
If you have a notebook the shortcut will be Control Key + Fn (Function Key) + F1.

Word screen without Ribbons displayed

Control + Fn (notebook) + F1 turns Ribbons back on.

Gerald Reiff