Hi @Max6, welcome to the Community! Thanks for the details about the issue and your setup - this is very helpful. Can you please confirm that you used the same Apple ID for your djay subscription and for your Apple One subscription?
If so, please try closing djay and the and logging out of Apple Music in the Apple Music App.
Then log out of your Apple ID in your iOS settings.
Reboot you device, log back into your Apple ID, launch djay and try logging into Apple Music only within djay.
Thanks for confirming @Max6. Can you please share a short screen recording showing that the Apple Music standalone app is working as expected and your process for attempting to log into Apple Music from within djay? I want to make sure I’m not missing anything here. Thanks!