Missing recommended iTunes
In order to submit your feed to iTunes, there are a number of elements which should be present, including <language>, <itunes:category>, and <itunes:explicit>.
If you are including iTunes elements in your Atom feed, add an
xml:lang attribute to the
feed element to satisfy
the language requirement.
<feed xmlns='http://www.w3.org/2005/Atom' xmlns:itunes='http://www.itunes.com/dtds/podcast-1.0.dtd' xml:lang='en-US'>
Consider adding the recommended element.
Not clear? Disagree?
You might be able to find help in one of these fine resources.