Feed items changed after upgrading

I have a news page with just a listing of headlines. Once I upgraded and installed feed to post my regular news page isn’t working.
I still want the feed to post functionality, but the page where I just have the news items displayed via shortcode no longer works. Once I go there I get the following error.
This XML file does not appear to have any style information associated with it. The document tree is shown below.
I would like that page to resume its functionality before I upgraded and installed feed to post, but I still want the ability to import posts to feed but in a different area of the site.
Hope this is clear?

The page I need help with: [log in to see the link]