Mailchimp - WordPress rss feed not valid

When trying to create an RSS-enabled campaign in Mailchimp, I get the error below. My RSS link is https://www.hackisition.com/feed/ .

https://www.hackisition.com/feed/ is not a valid RSS feed.

      

        
        
        
      

    

The link seems to work in my browser and a green padlock appears. I think it has to do with SSL. If I try to check my RSS feed , this is what happens:

Server returned [Errno 1] _ssl.c:504: error:14077438:SSL routines:SSL23_GET_SERVER_HELLO:tlsv1 alert internal error [help]

      

        
        
        
      

    

How can I fix this? I am using Nginx on the server.

EDIT . It seems like CloudFlare is the problem. See one solution here .