The message coming up is about the Buliding Blocks.dotx template? This is a known recent bug in Word. The message comes up any time you
use any building block. It only indicates some use, it does not necessarily mean that there have been any changes. It has nothing to do with the
Normal Template and is an erroneous message.
You can answer to save the changes. You can't get rid of the message untill Microsoft fixes the bug.
Here is
the thread about this on the Microsoft Answers site. The bug is in versions 1910 and later.
This is my page on Building Blocks:
Automated Boilerplate Using Microsoft Word