I'm having the same problem. I don't see this selection option on my iPhone 11, but only when using CarPlay in my Ford Fusion. The 'My thumbs up' station is selectable, and it shows all of the songs available. However, when I select either the Random button, or Play on an individual song, there is no sound (it does show a count down on the songs remaining time as if it is playing). I can change the channel back to any other station, and it will play music. Going back to the 'thumbs up' station still does the same thing. It displays progress, but no sound.
Moderator Edit: Changing title for clarity
As a Plus subscriber, you'll first need to activate a Premium Access session prior to connecting to CarPlay in order to listen to on-demand content. If the Premium Access session ends, you'll need to enable a new session in order to continue to listen.
For 'My Thumbs Up' station, do you mean Thumbprint Radio or a 'My Thumbs Up' playlist?
Let me know.
Use your mobile device only when conditions allow and as permitted by applicable law.
I double checked the Pandora account associated with your community profile and can confirm that it is currently upgraded to Pandora Plus, billed $4.99 per month.
Here are the benefits of Plus:
Is it possible that you have another Pandora account that is upgraded? If so, let me know and I'll message you privately to gather more information.