Game Client Lost its connection to server
About an hour after posting this it works again. Without me changing anything. It is a mystery.
When people say “the cloud” they really mean “other people’s computers”; sounds like what happened in your case is that one of the dozen or so routers or computers between your client and the ANet servers had a problem.
Then the problem was fixed, but whatever third party unrelated to either of you that runs it. Which was this strange, “nothing changed on either end”, problem that just went away.