If your shuttle was tracking, but now it seems stuck in one spot, it may have lost connection. To re-establish the connection, your driver just has to close and reopen the app.
To close the app using an iPhone, double-click on the "home" button at the bottom, and then swipe up until ShuttleControl is no longer on the screen.
To close the app using an Android phone, click on the square at the bottom right of the phone. Next you can swipe it off the screen, or just press X.
Once that's done, click on the ShuttleControl App to reopen it. This will reset the driver's location.