Generating Sample Data on Custom Print - No Data

I am creating a custom print in BI Publisher using the Microsoft Word Template Builder add-in.

I have navigated to Configuration > Custom Prints and Reports. I added a new custom print with an internal data model. I went to the Sample Data tab and clicked Generate to create the sample data. I get no data in the XML.

I then created a custom report on the same BP with an internal data model. I went to the Sample Data tab and clicked Generate to create the sample data. I got data in the XML.

Why am I not getting data in the custom print sample data set?