Maybe it's a certain number of traffic needed before it starts showing? Not sure...
Tracking code changes needed (as of Jan 22, 2014, 11:35:49 AM).
Your Analytics tracking code does not include the necessary support for the Demographics and Interest reports. Learn more about the simple, one-line, one-time change to your tracking code to add this support.
Did it ever give you Interest/Demographics data for that site/property (like do your reports show it happening day to day, and then just stopping)?