There are a few known issues that may be affecting your Kickr.
One of the main ones, your Kickr may not change resistance correctly if you’re also running other fitness apps at the same time.
When you have a moment, please exit Zwift and any other fitness software you have running. If you have your Kickr paired in any other software aside from Zwift, please unpair it, then exit.
Use your official support app to check for new firmware updates and complete a new calibration. Afterward, if need be; unpair your Kickr from the official app and exit it.
Finally, double-check that no other apps are running, then load up Zwift. Try to skip calibration in Zwift itself, but give it a test ride. If you’re still noticing resistance issues, please submit an email support ticket to email@example.com and attach any log files you have.