Chapters are all numbered "1" - how to fix?

Hi - new user here. I've been exploring InDesign CS5 for a few weeks now, and I'm starting to understand how it works. However, I'm having what I'm sure is a simple issue that I need some help with.

I've got a master page set up, and on that MP is a text frame in which I've done the Type>Text Variables>Insert Variable>Chapter Marker routine. A "1" immediately appears in the text frame.

I've used this document to create a dozen other documents, with the intent of pulling them all into a book. The book numbers the pages correctly from chapter to chapter, but every chapter is numbered "1."

What have I done wrong here? What's the best way to go about fixing it so the chapters are numbered consecutively?

Thanks in advance for your help.