So today, I tried to join an Italian friend's Just Dance Now Dance Room and by entering the code, the PC screen of Just Dance Now does not revert to that room. Honestly, I was duped. I knew that joining other friends for Just Dance Now was a hoax all along. I knew no one can do that. It's a discontinued.
If you're running into issues joining a friend, please head over to Ubisoft Support and they'll do their best to help you find a solution. We also have a handy FAQ for any other questions you might have regarding Just Dance Now!