When you register a custom template DNG the template will appear in the Reports->Generate a Document-style report and in the “Quick Print” menu.
This may seem convenient but it is actually a problem since the Quick Print ( Generate a Report for this View) menu is not functionally equivalent to the Reports one for custom reports.
The difference between using one or the other is in the URL that DNG will configure the report with. The URL ( the data) set by DNG’s Quick Print function is the URL for the current view and not the URL of the module or of the selected artifact(s). The view data is meant to be used with templates using the View schema of DNG but as that schema is private no custom templates can use it, only OOTB ones do. So as the data will not match the template schema the reports will always be empty.
Until this issue is fixed and custom templates are hidden from the Quick Print you should not use custom templates from the Quick Print option of DNG. All custom templates should be used from the Reports->Generate a Document-Style report menu.