The problem is that you do not have Heading 1 style with automatic numbering applied to your heading. I would bet on it.


The numbering must be set up following the instructions given here:
How to create numbered headings or outline numbering in Ribbon Versions of Word by Shauna Kelly


With your next response, attach a copy of the document, purged of confidential material with at least the cover page for your Chapter 3.


How to attach a screenshot or file in this forum.