Fixed layout ePub: Endnotes numbers in text linked to their endnote refs?

Kia ora,
OK so I've trawled for answers to this a fair bit, and I've done some testing, but I can't find a comprehensive answer and it is doing my head in!
I am designing (in InDesign CC) a fixed layout ePub that will also be exported as a pdf (it's for a journal – the ePub will have some embedded video/interactivity, and the pdf will have (most likely) have links to Vimeo content in lieu of this). Anyway, in my file, if I export a pdf, the endnote numbers link to the endnote text automatically. In the ePub, they don't link at all. I thought this might be an endnote vs footnote thing, but trialed footnotes and they don't link either. Does a fixed layout ePub just not support/automatically do this? Is there something I haven't ticked somewhere? Would I have to go in and manually make text anchors at each endnote and hyperlink them to make this work? (I have several images with captions and where these are mentioned in the text I've used text anchor/hyperlink to create a jump to the image caption in question). 

Any advice gratefully recieved!

Ngā mihi