This is most likely caused by a connection problem between the app and the PIVOT sensors. 

If you run into this:

  1. Restart the sensor marked H by holding the power button down for 2 seconds, releasing, then holding it down again for 2 seconds.  
  2. You will probably also need to go the Wi-Fi settings on your iPad device and make sure the PIVOT network is selected.

Once you've done these two things, the PIVOT Tennis app should start displaying your movements again.