Podcast RSS Feed Error Message

The fact that the error message was received soon after posting indicates that it's not a problem with the content of the episode, which has to be assessed manually, which takes time. Your feed validates in three separate validators: the only problem I can see with it is that you have a category - 'Religion & Spirituality' - but no sub-category. I wouldn't expect this to be a reason for rejection - what usually happens is that you get a sub-category added for you, which may not be the one you want. You should add one from the list at:

https://help.apple.com/itc/podcasts_connect/#/itc9267a2f12

Other than that I can't see what could be causing this: it could be a bug at Apple's end, which is rare but not unknown, and if adding a sub-category doesn't work (it probably won't) you should contact Support, emphasizing that the feed has passed validation in three validators. Go to https://itunespartner.apple.com/en/podcasts/overview and click the 'Contact Us' link at the bottom of the page.

Podcasts Connect says your feed is 'prepared for submission', meaning the feed is technically OK but you haven't submitted it yet. When you submit it you should, fairly promptly, get a message acknowledging the submission. You say you got an error message - was this pretty well immediately after submitting? and what did it say?