Sample Data isn't populating for the Debugger

The debugger itself is the only thing that will automatically create Sample Data for flows. When Remember to the Recent List is checked under System > Settings > Designer Studio Settings, the debugger will save flow input data. If you want to expose the data from live flow executions that ran outside of the debugger, you will need to make use of a Log step, Send Email Step, or have a data type specifically made for capturing that data.