I have the kinect bundle and I get these error message as well...
I have just dance 2020 along with the unlimited package with xbox one s and kinect and for the last two days since I subscribed to the unlimited package I can't connect most of the time and the internet connection is just fine. I chatted for a very long time with a chat supporter here in ubisoft and he couldnt help and said he will try and get help from the "just dance" team. I still didnt get any answer.
I have just dance 2020 and the unlimited is not working....so its not just 2021