I keep getting the timeout when I am adding multiple names. But If I just add a single domain at a time, then it is okay and performs the http-01 challenge fine. But more than one, it fails and timeout message.
Overzealous DDoS protection?
Overloaded web server?
Aliens "capturing your packets"?
[Of course we can only guess wildly until provided with sufficient detail as to allow for a more educated guess]