I have narrowed down the problem even further. I tried out BigRingVR. BigRingVR’s app only supports ANT+. Got the same behavior I was getting in Zwift; pedal resistance did not vary with road grade while using ANT+. Went back and reviewed all the Amazon reviews on the ANT+ dongle I am using. Sure enough, I found 1 review out of the 400+ that says dongle does not support ANT+ FE-C (Fitness Equipment Control).
[Here is where I would have inserted a screen capture of the Amazon Review, but I am not considered worthy to add “mutli media” elements to a post.]
I have contacted the manufacturer (CYCPLUS) to confirm the dongle does not support FE-C. CYCPLUS says the device supports FE-C. However, BigRingVR set me a link of analysis of the device done by the fitness equipment manufacture Tacx (t a c x f a q x . c o m /knowledge-base/cycplus-ant-stick/). Tacx found the device lacks important functionalitywhich causes problems controlling fitness equipment.
[Damm, not even authorized to include a html link in a post.]
So why did I think it should have worked? Consider the following screen capture:
[Here is where I would have inserted a screen capture showing the “Controllable” being connected via ANT+ FE-C]
Zwift appears to have successfully connected to the “Controllable” part of the Wahoo Kickr using the FE-C protocol. It connects something but Zwift clearly never validates the connection for FE-C operability. The log file probably is full of Zwift sending commands to increase/decrease pedaling resistance without ever getting back confirmation that the command was accepted. Zwift should have generated an error/warning right from the start indicating there is a problem.