It can’t be enabled for some reason.
FYI: The same thing happens for me with OpenMRS 2.3.
You click the button to start the app. It says it has "Successfully enabled referenceapplication.personalRelationships. Refresh the list, and it’s still marked as “disabled”.
I’m having the same problem, and it seems to prevent me from customizing my registration app. Did you ever solve this?
No, I don’t think I ever got it to work right.