
It was only when I clicked on the "Normal Text" setting in the upper left corner of the screen next to the "Equation" dropdown (while in Equation Editor), to turn OFF Normal Text, that the shortcut of "SHIFT" + "_(subscript)" actually worked. When you are using Normal Text, the "SHIFT" + "underscore and subscript" + "space" that everyone else had shared does not work.

However, most of my formulas in physical science use "Normal Text" (text that is not italicized).

I use Word 2013, and write out a lot of tests for math and physical science, which include many formulas with subscripts.

I have tried everyone's suggestions, and nothing has worked, but I finally figured out what was going on.
