Subscribe to this feed link not working for everyone

I have the Hueman theme. As part of the theme options, it has “Social Links” you can add to the site. I added the rss icon for “Subscribe To This Feed” and inserted the url, which for my site is: https://nashvillethreesixty.com/feed/. I tested it on my site and when I clicked the icon, it opened the feed in a separate window and the box popped up with the option “Subscribe To This Feed”. I did and if I click the icon now, the feed loads perfectly. However, I did check the box asking for email updates when new content is loaded and I haven’t received any despite there being new content. The bigger problem is that several of my friends have tried to subscribe and they get a message that says “This XML does not appear to have any style information associated with it. The document tree is shown below.” Below that, they get the text code for the articles instead of the articles they can read. I suspect a feed reader problem but have no idea how to go about fixing that. If anyone has any suggestions, they would be greatly appreciated!! Thank you!!

Here is the link to the site: https://nashvillethreesixty.com/

Bev Miskus