NetBeans UML reverse engineering has never really worked well, I don't think it's supported in the later versions anymore. Not by default anyway.
I do wonder though, what IS the relationship between your classes? UML shows the inheritence between objects, and most of your classes seem to be pretty independent? They do not extend any other classes?
Your best bet would be to import into into ArgoUML
and set up the links yourself if it does not create them by default.