Solution
When you run your main VI and it calls the subVI, the stop button for the While Loop is read (false) and that false value is passed to your subVI. This value will keep your subVI running until you manually stop it. The connectors on a subVI are not user controls, the are more like initial conditions in which you start your subVI.
If you want to have a LabVIEW VI running constantly and updating values in a subVI, you can use a While Loop structure in your main VI but not in your subVI.