Ultrasonic Rangefinder Sample Code

Can’t figure out how to get the rangefinder talking to the brain. We have looked at other sample codes and nothing posted is working for us. Before the int main() we have:

sonar Sonar=sonar(Brain.ThreeWirePort.A);

then in the int main() we have:
Brain.Screen.print(“Distance : %f”,Sonar.distance(distanceUnits::cm));

and are expecting a distance in cm to be displayed to the brain screen. We get distance: 0.000000. Are we missing something?