Fields from Related Modules in Reports do not show up.

Hi, I am preparing a custom report from the Cases module (where we register visits to our development) and the Potentials Module (which is linked to the Cases Module through the Potential Field). Even though I can choose columns from the Potentials Module to create the report, when running the report the fields that belong to the Potentials Module appear blank, and only date from the Cases Module is displayed. Can anyone help me figure this out?

Thanks

Manuel