My Feed Only Shows 10 Episodes
Your podcast feed is managed by Seriously Simple Podcasting, however the # of posts to be included in a feed is something that is set in the WordPress admin dashboard. In Settings -> Reading you can set the number of episodes to be included in your podcast feed in the “Syndication feeds to show the most recent ___ items” field.
By default, this number is 10, which is why it’s common for new podcasts to only see the 10 most recent episodes in their feed. Set this value to whatever you’d like, and that number of episodes will be included in your podcast feed.