Several things.
Your display of your titlepage.xhtml is not complete, so that cannot be evaluated.
What I usually see in the content.opf (with your data):
Code:
<meta content="cover" name="cover" />
and
Code:
<item href="Images/cover.jpeg" id="cover" media-type="image/jpeg" />
Perhaps the coding has some issues with the extention .jpeg instead of .jpg, although that should work.
What does the validation do?