I'm on a Mac with OSX 10.11.6 and the NVIDIA GeForce GT 750M 1024 MB
Blender version is 2.78 RC.
I've attached an image of the error that pops up when I hit "login" with the addon. I have no way to use the ID addon or Cloud addon at the moment. It says there is no "requests" module.
Basically, I go to User Prefs, turn on the blender ID addon version 1.2 and type in my username and password for my blender ID. And that appears.