One of the reason this could happen ,if the grid is not able to push the metrics data to the database. Take a look at the grid.log inside CDP's tomcat/logs to find out if there are any errors reported related to database connection.
You try with below
-set the Record Metrics property to true for any process in developer studio on which you will report on
-export it to repository and activate it on the grid
-clear browser history and access your baodashboard to create report type process metric.