I added my RSS feed to Apple Podcasts and now my artwork won't pop up, preventing me from publishing

Once I added my RSS Feed, my podcast artwork won't pop up. Apple gives me the option to publish but once I click it, it says "Art - Artwork must be 3000 x 3000 pixels, JPG or PNG, in RGB color space, and hosted on a server that allows HTTP head requests." My episodes appear in the "episodes" tab but not in the "shows" tab. It still says it's in draft mode.

However, prior to putting the RSS feed, the artwork was there.

Here is my RSS Feed:

https://feeds.redcircle.com/551305ec-6867-4d63-9f20-f07697654de2