I get a "connection closed" error when trying to add the "http://csdl.computer.org/rss/annals.xml" feed (and a number of others). They work with RSSowl under Win 10. Any ideas
unfortunately I am not able to test the feed with OS-X Sierra.
I just tested your feed in my system (Windows) and it works fine.
You can modify the connection settings
Tools -> Options -> Network Connections.
You could f. e. try to increase the number of retries. The server seems to respond slowly.