Try using a different web browser. I was using internet explorer and getting the same message. I switched to mozilla and it worked the first time I logged in.
I guess I was not specfic enough. I can sign into my account just cannot sign in with the updater app even if I am signed in my account at the same time and tried while not signed in
Make sure CC is not running by stopping in task manager.
Navigate to: C:\Users\your user name\AppData\Local\Adobe\OOBE
Open CC and sign in.