You're using WishList member plugin. The feed is no longer available to the public. ?wpmfeedkey=2;aa6ebf258c9b3a40990e5cee498289bf allows you to see the feed, but without ?wpmfeedkey=2;aa6ebf258c9b3a40990e5cee498289bf just dualnetworking.com/feed/podcast/) directories like iTunes will get a 404 page. You will need to load this dualnetworking.com/feed/podcast/ feed in a browser where you're not currently signed into your blog to see the problem.
If you want to keep WishList member and also still have your podcasts appear on iTunes, you will need to search this forum for "WishList Member" and find instructions for using a define that you can add to your wp-config.php which will fix the problem.