"Thanks for contacting Blizzard Technical Support, my name is Jon.  If
 when logging in, you hang on "Authenticating" or any other similar
 connection problems, please wait 10-15 minutes and try again. In this
 particular case the login server was experiencing difficulties. When
 this occurs the game servers may still be up, so you may notice people
 playing while you are not able to get in.

 Occasionally servers will be taken down to update software or to make
 changes or enhancements to the hardware. If we find any problems that
 could contribute to server crashes, we will be taking action in order to
 prevent this. If we are forced to take down a server, we will get it
 back up and running as soon as possible. We appreciate your
 understanding in this and we will be doing everything we can to ensure
that your World of Warcraft experience is enjoyable and fair.
 
 I am sorry for any inconvenience that this may have caused you. This
 problem should be a temporary problem with our servers and should be 

fixed as soon as possible. When we do take the servers down, there will
 be a post regarding the outage on our World of Warcraft server status
 forum. https://forums.worldofwarcraft.com/board.html?forumId=11113

. This  forum will also be updated when the issue has been resolved."