We've created this Forum Thread with some workarounds and advice to assist you in publishing you ebook.
Open Office to e-pub tip: automated Heading CONTENTS can be a TOC problem
Working in Open Office, followed instructions, converted to rtf and to Word 1997/2000 (yes, ancient - all that Open Office offers, though)— converted to e-pub and the TOC was missing heaps in both cases.
Couldn't solve the rtf, but in the .doc, I traced the problem solely to where I'd used FULLY AUTOMATED Heading CONTENT. My H2s were just 'Chapter 1, Chapter 2.... Chapter 75', so I had automated the CONTENT as well as the style by going into Tools — Outline Numbering— and filling in the boxes, to automatically generate a heading in the format 'Chapter X'. Gets you automated correct numbering of chapters— way to go in a big document.
But— the resulting automatically-generated H2 heading, 'Chapter X's, were what the e-pub conversion couldn't see.
SOLUTION 1 (retaining automatic numbering of chapters)
Adding any further text to the heading by hand-typing into the document "revealed' the WHOLE resulting heading to the e-pub TOC. So —
(automated) Chapter X = ... nothing (in TOC)
(automated) Chapter X + (typed) Historical Background = Chapter X Historical Background (in TOC)
Even a typed full-stop was enough to 'reveal' the whole heading to the e-pub conversion (though the spacing was odd).
Sadly, a nice invisible space-bar stroke DIDN"T work.
SOLUTION 2 (losing automatic numbering)
SInce I was finished with all major editing, I sacrificed my automatic numbering of chapters and, using Navigator in Open Office to call up my heading for me, whipped through them all, deleting the automated 'Chapter x' and then pasting 'chapter' and typing the number into the remaining formatting space. Only took five minutes, and Nav bar will allow me to keep an eye on my chapter numbering in future anyway. e-pub generated my TOC perfectly.
??SOLUTION 3?? Looks to me like converting fom Open Office to a more recent version of Word probably solves the whole problem anyway. For penny pinching Mac users like me, though, the above two solutions may help.