This is the default message from a Custom Java Action that hasn’t been written.
I suggest looking in your logs, it should say the name of the action with the problem and you can look there to fix it.
Good luck!
I suggest that you start fresh.
once you install the module quit the modeler(studio pro)
open the project any java project IDE like Eclipse.
Build the project in that IDE. (if you wish then you can check the java codes too inside the EmailModule package)
Then open the modeler and run the project.
Good luck