Thanks for sharing details about the issue here. I know how challenging it is when you're having issues playing music on your speaker group. To confirm, are you able to play that specific song on your speaker group? Are you able to cast it in the group? Does the same issue happen when you use the Google Assistant app on your phone?
Looking forward to your response.
Chiming in to see if you still need assistance with this. Hope the previous post helped. Let us know if you have additional questions, otherwise we’ll be locking the thread.