I’m having the same problem (iMac 2011 / OS X 10.11.1 GM) - but the MyCloud drive is new yesterday since I installed the GM so I don’t know if it might have worked on earlier releases.
I am able to connect using the “Command+K” and “afp://wdmycloud.local” using both guest and a user account which I created with a password (trying both a unique password and the same password as my user account to simplify auto connect)
I can say that I also have a MyPassport Wireless that does auto-magically connect in Guest mode from the “Shared” section of the Finder, while the “WDMyCloud” server does not.
I’m not sure if it’s sympomatically related or not, but TimeMachine to the drive seems interminably slow as well - in roughly the last hour the TimeMachine backup has only backed up ~350MB - BUT if I drag&drop a file into the mounted folder it goes much more quickly - a 1GB file copied in roughly 40s.
Both my iMac and the MyCloud 4TB are connected to the same Gigabit switch each directly wired, no router or WiFi is in the way.
