iTunes Connect Podcast artwork error (won't validate)

I am trying to publish my podcast on Apple Podcasts. I am using Podbean. When I try to validate my podcast on Apple, I get the following error message: "Podcast artwork must be between 1400 x 1400 and 3000 x 3000 pixels, JPG or PNG, in RGB color space, and hosted on a server that allows HTTP head requests."

My artwork is 302.53KB, JPG, RGB, and 1400x1400. My RSS feed is https://feed.podbean.com/readingduringrecess/feed.xml

Does anyone have any ideas as to why my podcast will not validate?

Thanks!