Activity Monitor % Processor Time grayed out on SQL Server

The *% Processor Time* graph at *Activity Monitor* for remote connections stopped working and it grayed out after the physical SQL Server restart (image below), but when I get in the server with the same Domain User it works fine. It was also working fine on remote connections before the restart and I have noticed that it takes significantly more time to load the Processes than before. The problem is happening to all users that try to see the Processor Time remotely including **sa** and server admins so I would think it´s not a permission issue. The server runs Windows Server 2012 and SQL Server 2012. What could be happening? or How can I solve this? Thanks in advance! and sorry about my English.