What do you see (or not see) when you can't sign in to the Cloud... any of these?
Sign Out When Sign In http://forums.adobe.com/thread/1450581?tstart=0 may help
-and http://helpx.adobe.com/creative-cloud/kb/unable-login-creative-cloud-248.html
-and 'looping' https://forums.adobe.com/thread/1504792
BLANK Cloud Screen http://forums.adobe.com/message/5484303 may help
-and step by step http://forums.adobe.com/thread/1440508?tstart=0
-and http://helpx.adobe.com/creative-cloud/kb/blank-white-screen-ccp.html
Mac Spinning Wheel https://forums.adobe.com/message/5470608
-Similar in Windows https://forums.adobe.com/message/5853430