Adobe Acrobat Pro DC - Quick Tools - Save Command Does Not Display

In Quick Tools for Adobe Acrobat Pro DC, "Save" is checked on the "Show File Tools," but only an empty space, not an image, for the "Save" command is displayed on the Quick Tools bar.  The images for other commands, such as "Print," are displayed on the Quick Tools bar.  Indeed, the empty space for the "Save" command actually works to save a document if you click on the empty space (i.e., the image for the "Save" command merely does not appear, but the "Save" command is enabled).  This is true even if you edit a document, and this is not a situation where the "Save" command is greyed out -- there is no image at all.  See image of Quick Tools bar below.  I have "repaired" my installation of Adobe Acrobat Pro DC, but it has not solved the problem.  This problem only recently began, apparently after either a software update of Adobe Acrobat Pro DC or a software update of Windows 10 Pro.