Problems with feed (Can’t parse your feed. Invalid XML: Error on line 1: The markup in the document preceding the root element must be well-formed.)

I get

I did look at your feed previously and though there are one or two points, such as use of an obsolete category, there was no serious problem. The problem they flag would likely be a character in front of the very first tag, which would invalidate the feed, but there is no such character there.

XMLGrid.net reports 'Your feed appears to be encoded as "UTF-8", but your server is reporting "US-ASCII" ', but this shouldn't cause problems - however if you can, check that with Podcast Mirror. (The other feed doesn't have this issue.)

However as I'm getting it accepted and you are not I can't explain what's going on. You could try clearing your browser's cache, or using a different browser - this seems an unlikely explanation, but try it. Failing that, I can only suggest approaching Support. Go to https://itunespartner.apple.com/en/podcasts/overview and click the 'Contact Us' link at the bottom of the page. Make sure to explain that I got 'prepared for submission'.

Podcasts Connect is saying that the podcastmirror feed is 'Prepared for submission', meaning it's technically OK, so presumably you've cured the problem.