These flags should be available in the properties view of Gen Diagram under Gen Editor Generator in your .gmfgen. If setting them to true doesn't help (I suspect it won't as Eugenia does this by default) please send me a link to a zipped archive containing your code so that I can have a look.
i found the properties, which were set to false. They are not directly under Gen Editor Generator but in the Properties from Gen Editor Generator->Gen Diagramm xyzEditPart. Maybe the tutorial should be updated. I searched a lot :-S
Well, there is still a question about this: Why do i have to set it manually?
The tutorial sais "If you have not implemented your editor using EuGENia, before you start please make sure that you have turned on validation in your .gmfgen model.". I'm always using Eugenia and have a validation-project as described in the tutorial.
I also take one constraint from the tutorial just to be sure not to make a mistake in EVL.
It looks like that i missed one (simple) point. If i validate nothing seems to be happen... :-S