Is the text really not there, or is it just colored white?
The TOC option in ePub export dialog is relevant to the ePub navigation panel. In the screenshot, we're just seeing the book's TOC page as it is rendered in the ePub. My first guess is that it somehow has aquired white coloring. Maybe it's a missing glyph thing too. Perhaps the font embedded in the ePub doesn't have these small-caps, and so is showing blanks? (But then the chapter numbers on the left are showing up and they are also small-caps, so not sure about that.)