I have a Kickr Core and everything works perfectly. I agree with previous commentor about erg vs. resistance. After you Load the workout you want to do, click on Devices at the bottom right. That should show the Kickr Core attempting to load (or being loaded). Click on the Kickr Core and it will tell you if you are in Erg or Resistance and give you the option to do a Calibrate Spindown. It will only do the spindown in Resistance or Standard. If this is already in Resistance, I suspect that you Wahoo App got switched to Erg when you dropped Zwift. You should double check this as well.