If you own a HomePod and don’t have an Apple Music family account, your music listening experience is going to get a bit more restrictive. Apple is no longer allowing HomePod owners to stream different tracks on their HomePod and on their iPhone simultaneously.
If you are playing music on your iPhone or iPad and start playing music on your HomePod, Apple Music will stop streaming music to your iPhone and vice versa. The same behavior is also going present if you are playing music from Apple Music on your iPhone and try to listen to stream songs from Apple Music via iTunes on your Mac. Its a seemingly small change but one that is definitely going to trouble a lot of users.
Essentially, Apple is now only allowing one stream at a time from a regular Apple Music subscription.
As per Apple customer support, it should not have been possible in the very first place for users to play music simultaneously from Apple Music on their iPhone and HomePod. It was possible so far due to a bug which Apple has now fixed. Apple had never advertised the original behavior through its marketing materials.
The solution to this problem? Subscribe to Apple Music Family plan. The regular Apple Music subscription allows for playing back of one stream at any given time. Upgrading to Apple Music Family plan increases this limit to six streams.
Apple seems to have made this server-side change very recently as most HomePod users have started complaining about this issue in the last few days.