Sorry to hear about the trouble with adding YouTube Music to your device. I wanted to check in, and see if I could be of some help. I did find an article with some troubleshooting steps related to your issue. Please let me know if that helps, or if you have any questions from here.
I haven’t heard back, so I'll be locking this thread if we won't hear back from you again in 24 hrs. Feel free to create a new one if you have more questions or have other concerns in the future.