Diagnosis
The article/unit of measure combinations assigned to the family couldnot be locked.
Another family, which may contain several articles from your family inthe same unit of measure is currently activated. To avoid multipleassignment of articles to active price families activation was notperformed.

Procedure
Try to activate the family again at a later stage. Pay attention to anymessages in the activation log. If you do want to save the family youcan deactivate it and then save it.