Feed showing up empty

I tried to add a new feed and it displays the title as “Untitled” and says there are no posts to display. But I know that there are posts (I can see them on the feed’s website). Not only that, I signed up for another feedreader and added this same RSS feed to it and it displays perfectly. Any idea what’s wrong? I prefer NewsBlur to this other feedreader (it is very limited unless you pay), but I don’t understand why this one feed won’t add.