I’m using the latest version of the Android App connected to my KICKR with the latest firmware. ERG does not work in workout mode or in free ride.
I am seeing this same behavior as well. I have a KICKR, Pixel 2 XL, and a Pixel C Tablet. Sensors work and are paired, but ERG mode does not change resistance, when riding a workout. Tested with SST - Short workout in Zwift.
My “normal” method of Zwifting is with an Apple TV, and that controls the KICKR just fine.