on all my epub going to toc takes me to the end of the book, like a different section (in other words if the book is 400 pages, it will say page 1 of 1 but you can see the slider at the bottom is all the way to the right, so really it is like at the end of the book), but then the page just has a blue link that says "cover" and hitting that takes me to the cover at the beginning of the document.

same document on .mobi though will in fact take me to the toc.
so it seems either it just does not have the toc for epub or at least I I can tell.