Wordpress RSS on Ubuntu 20.04 now working

I have a bunch of wordpress sites that I have been running on AWS under Ubuntu. I decided to move them to my own local server.

All the sites moved fine except one that used an RSS feed to feed Mailchimp to send out a newsletter. The site works fine on the AWS server and fine on my server except the RSS feed does not work.

From, reading, I am under the impression that RSS uses port 80 which is open on both servers, as well as port 443. Both servers use https fine.

I tried using a new install of wordpress on my server, and it does not work either, making me think it is something to do with my server.

This feed works: https://potlatchga.com/feed/ --- This is an aws server

This feed does not work: https://potlatch.dyns.com/feed/ --- This is on home server

I am testing them using the rss validator.

I have been pulling out my hair the last few days trying different versions of php (7.4 and 8.0) and php extensions. I have run out of ideas. I am using the latest wordpress download.

Surprisingly little info on Wordpress RSS feeds, except they usually work!