Simplepie not recognizing wordpress feed

I am using simplepie on my website (not wp) to pull the latest post (from wp blog installed on the same site) as sort of a “latest news” sort of thing. I can see the feed when I go to the url in my browser, but Simplepie will not parse it for some reason. The code works on the simplepie end because I can get feeds from other blogs, including another one that I have, but not the one that I need.

Is there pre-requisite code in the theme for using simplepie?

WordPress is already creating the rss feed anyway so I don’t see why it would need more than that.

Thanks for your help in advance.