Occasionally you may notice the the Advanced Document Automation button icon is grayed out.
This situation can happen due to one of two issues:
The document you're opening is a ".doc" file instead of a ".docx" file.
The document you're opening is in "read-only" mode.
The simplest solution to both of these scenarios is to make a copy of your document and make sure you save it as a ".docx" file instead of a ".doc" file. Open up the new document and the Advanced Document Automation button should become active again.