Non functional RSS feed?

I recently submitted my site for Apple’s News app and received the following note from them…

While reviewing your application to distribute Clean Slate Farm on News, we noticed that something isn’t quite right. Please resolve these issues, and then resubmit your application at News Publisher.
At least one RSS feed isn’t functional.

I ran the URL through WC3 validator and it says Congrats, all is well.

Does anyone have an idea what this could mean?

Thanks

Dave
https://cleanslatefarm.com