Exporting Epub dialog box only shows "default" style

When I attempt to export my book doc (26 chapters) to Epub, I click on the "Navigation TOC" window and choose "multi Level (TOC style) rather than "file name". . .Then I go to the TOC style window but it only gives me the "default" option, the saved style does not appear as an option. When I export to epub and open the reader. . .the reader's table of contents only shows the file name, such as "Chap-1-6-9-ind-1" rather than the chapter number and title such as "Chapter 1  The Two Houses" Why only "default" is available in style window??