Each data source is licensed individually, so not all data sources may be available in your installation.
To find out which data sources are available in your installation, select Help -> About Enterprise RTView in either the Display Builder or the Display Viewer Application.
If the datasource appears in the help window, then the error you see generally occurs when the environment for the RTView is not setup correctly. Please view the Setup section in the RTView User Guide and setup all the environment variables as required by RTView.