Hello,
Thanks for trying to answer. As this unfortunately didn't give me more details than the cryptic error messages from Itunes Producer , I spent some time on my own comparing the OPF with files from other books and finally managed to edit it in the right way .
(my metadata was complete, I had just put in some temp text in place of author & title)
If anyone going through the same process has similar issues, I have posted below the corrected OPF. (note : Calibre is unfortunately not a solution as it doesn't convert my epub to something accepted by Itunes Producer.)
I only have one remaining issue now which I'll detail in another thread.
OPF :
<package xmlns="http://www.idpf.org/2007/opf" unique-identifier="book-id" version="3.0" prefix="rendition:
http://www.idpf.org/vocab/rendition/# cc: http://creativecommons.org/ns#">
<metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
<dc:title>MY TITLE</dc:title>
<dc:creator>AUTHOR</dc:creator>
<dc:date>2014</dc:date>
<dc:language>fr</dc:language>
<dc:identifier id="book-id">MY BOOK ID</dc:identifier>
<meta property="dcterms:modified">2012-05-09T08:58:00Z</meta>
<!-- FIXED-LAYOUT METADATA -->
<meta property="rendition:layout">pre-paginated</meta>
<meta property="rendition
rientation">portrait</meta>
<meta property="rendition:spread">none</meta>
<meta name="cover" content="img-cov" />
</metadata>
<manifest>
<item id="ncx" href="toc.ncx" media-type="application/x-dtbncx+xml" />
<item id="nav" properties="nav" href="nav.xhtml" media-type="application/xhtml+xml"/>
<item id="css1" href="template.css" media-type="text/css" />
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<item id="p3_css" href="p3.css" media-type="text/css" />
<item id="p4_css" href="p4.css" media-type="text/css" />
<item id="p5_css" href="p5.css" media-type="text/css" />
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<item id="p7_css" href="p7.css" media-type="text/css" />
<item id="p8_css" href="p8.css" media-type="text/css" />
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<item id="coverimage" href="images/Cover.jpg" media-type="image/jpeg" />
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<item id="page31" href="images/BG_p31.jpg" media-type="image/jpeg" />
<item id="page32" href="images/BG_p32.jpg" media-type="image/jpeg" />
</manifest>
<spine toc="ncx">
<itemref idref="item01" />
<itemref idref="item02" />
<itemref idref="item03" />
<itemref idref="item04" />
<itemref idref="item05" />
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<itemref idref="item30" />
<itemref idref="item31" />
<itemref idref="item32" />
<itemref idref="nav" linear="no"/>
</spine>
<guide>
<reference type="Cover" href="p1.xhtml" title="Cover"/>
<reference type="chapter1" href="p2.xhtml" title="Chapter 1"/>
</guide>
</package>