Many thanks for your suggestion and support for TrainingPeaks Virtual.

The tilt function on a Kickr bike is entirely controlled by the embedded Kickr trainer - TrainingPeaks Virtual tells the Kickr Bike what gradient to simulate and then the Kickr bike both sets the resistance to be appropriate for that gradient, and the tilt. Specifically, the Kickr bike does not allow third party applications to control the tilt directly...it does it itself.

If the tilt is not working for you, then it is very likely that the Kickr bike is simply not in tilt mode, and is locked to be in a level position. If you unlock it, then it will tilt.