I have again been in contact with Protopage, they contacted you using the contact form on your web site, under the category "other"
The message they are trying to send is
Hi, please could you forward this to your web site engineers: your official RSS feed URL https://www.flyertalk.com/feed is blocking the Protopage.com feed indexing server with a 1005 error code. Please could you investigate and unblock our feed indexing server, which has a user agent "Protopage/3.0 (http://www.protopage.com)"
They can be contacted via [email protected]