Issue exporting to vellum

I am trying to export a 10 chapter book from Scriv to Vellum. Although I have ticked each chapter and selected Vellum export, the book exports to Vellum as a single, long chapter.

I am using 3.2.3 on a Mac running High Sierra.

Where have I gone wrong? Thanks!

Vellum needs clues, like page breaks and centered or bold headings, for dividing the project into sections. Do you have any? If you do, and Vellum doesn’t get the hint, that’s not a Scrivener issue. A simple fix in Scrivener could be just to make each chapter a folder, not a text file.

Thank you! Will give your suggestion a try. I appreciate your help.