shareplay, CarPlay

On my Macs and all devices, I have Apple Music but without active susscription. Perhaps one of you can answer my questions. Do I need BOTH an active Apple Music subscription and SharePlay in order to play music from my iPhone on my CarPlay-equipped car? I recall being able to do this recently, but not now. SWHat happens is I get a connection I the car and I can see music items in the Media panel apparently ready to play, but nothing but a momentary switch between the Play icon & he playing one. Thanks I advance for any informative help.I have iPhone 17.3.1 running & CarPlay is always up to date.

--Gene