I'm trying to create a navigable TOC that appears in my book as well. I set up a TOC style with "Make anchor in source paragraph" box checked. But when I import, I get an error message that some TOC links aren't working because I need to check the box "Make anchor in source paragraph". I've done this 8 times, each time the box is checked and each time it tells me it isn't. That means the TOC doesn't even show up on my epub.
I've also tried taking my automatically generated TOC and convert it to text and paste it back into the document, without any links or anything. It still won't show up and I still get the message "Make anchor in source paragraph" isn't checked in my TOC.
Finally I went through and typed out the TOC and then made links with text anchors. I still get the same export error. This is driving me nuts.