It seems your TOC is empty. Try this "minimal" NCX:
Code:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE ncx PUBLIC "-//NISO//DTD ncx 2005-1//EN" "http://www.daisy.org/z3986/2005/ncx-2005-1.dtd">
<ncx xmlns="http://www.daisy.org/z3986/2005/ncx/" xml:lang="en" version="2005-1">
<head>
<meta name="dtb:uid" content="the book id" />
<meta name="dtb:depth" content="1" />
<meta name="dtb:totalPageCount" content="0" />
<meta name="dtb:maxPageNumber" content="0" />
</head>
<docTitle>
<text>Title</text>
</docTitle>
<docAuthor>
<text>Author</text>
</docAuthor>
<navMap>
<navPoint id="Book" playOrder="1">
<navLabel>
<text>Title</text>
</navLabel>
<content src="filename" />
</navPoint>
</navMap>
</ncx>