The app must receive data through your mobile network to work. The app will become unresponsive if this setting is turned off. Here are some resources:

iOS: Go to Apple Support to learn how to check your cellular data usage.

Android: To update the mobile data settings:

  1. Go to Settings
  2. Then Applications
  3. Select the CAR app
  4. Then Mobile Data
  5. Tap Background Data
  6. Make sure it isn't toggled to "Always"