Thanks for all your help on this, man. The first thing I did was search for similar fixes, and tried a couple that didn’t work — I should post links to that on all the pages where I found other people struggling with this same thing!
Try to change your plugin. You must do research before choosing any plugin for rss feed. I suggest you to go through this article to properly setup your rss feed https://www.wpblog.com/best-wordpress-rss-plugins/
I am having error message RSS feed in my website. I have already deactivated my theme and activated default theme but that’s not working. I have seen some good ways to fix RSS feed errors define here https://wpitech.com/how-to-fix-wordpress-rss-feed-errors/ . The issue is not resolving I am still having message error.