Century Gothic Font

I have hundreds of documents that are using the Century Gothic font. When I open a new document from a current document that is using Century Gothic it opens with Century Gothic as that is the default I set in settings (see screenshot).

HOWEVER . . . when I try to open a new document directly from the app, Century Gothic is nowhere to be found in the dropdown nor is it in the Font Book. How can this be? As I noted above, I can pick it when opening a new document from an existing document!

How can I PERMANENTLY add this to my Font Book for universal use?