Click the Advanced button. Is the Start New Chapters... ticked? Try clearing that.
See www.grainge.org for RoboHelp and Authoring tips
@petergrainge
I've been poking around a bit more. Here's the deal.
New chapters will always start on a new page and have a next or odd page break according to the Start New Chapters setting. If ticked it will be an Odd Page break, else a Next Page break.
Topics within a book will follow the Start Each Topic on a New Page setting. If ticked, each topic will be separated by a page break, not a section break. Else they will be on the same page with no breaks of any type.
Topics not within a book will be followed by a section break.
So section breaks are only created for chapters and topics not in a chapter.
Hope that helps. Please post back if you find otherwise.
See www.grainge.org for RoboHelp and Authoring tips
@petergrainge