EPUB eBook Creation for D2D

I converted my Kindle Mobi file to EPUB by Calibre and uploaded it to D2D, but D2D tells me that the epub file was not properly formatted. "All of the text is within two files inside the book: titlepage.xhtml and index.html. And my epub's NCX only has two entries in it: Due to this, the textual ToC within the file cannot be built properly.” A few other items also did not convert properly. I need someone to fix the problem.