Insert symbol has disappeared

[Gypsy Moth]

Insert symbol has disappeared from my drop down menu. As well, when I tried
to put in a shortcut for an em dash the result was an empty space on my page.
I've switched to a new computer but I dont' think this should affect these
options. How do I get them back?

 

[Suzanne S. Barnhill]

See http://sbarnhill.mvps.org/WordFAQs/LostSymbol.htm for an explanation and
remedy.