I activated the All In one SEO sitemap feature and overall it does appear that most of my content is being indexed.
However, when I go into Google Webmaster tools it shows I have three errors for the sitemap. They are as follows
Missing XML tag
This required tag is missing. Please add it and resubmit.
Parent tag: urlset
Sitemap is HTML
Your Sitemap appears to be an HTML page. Please use a supported sitemap format instead.