You may be posting in a post-type called sermons instead of a standard post.
If that is the case, you *may* want to enable post-type podcasting. Check the box at the bottom of the settings page. Then you will see a menu item below powerpress in the sidebar called post type podcasting.
Go in there and add your post type "sermons" or whatever it's called. This will give you a new feed address that should have all your posts in it. (or at least the last 10 or so)
Post-type podcasting is a bit complicated but once it's setup, it works like a charm.
-Mike