Hi everyone! I had the same problem but it appears to be fixed now. First, I went into settings found apple music and turned it off (I think this is a new option). Then, I did the same hard reset suggested in earlier posts. Lastly, I just went into Spotify and began playing music and it automatically picked it up in the control center and lock screen. Good luck!!
Did you try turning off apple music in the app yet via settings? Then just turn on Spotify. I also opened the control center while spotify was running and the control center began to pick up the music I playing.