I have two iOS devices I use with Carplay/Pandora. One is an 11 Pro Max running iOS 14.x and sometimes when I use Pandora it'll allow me to see and choose specific songs in a playlist on the head unit. This is new as of sometime last fall I believe. I also have an older iphone 5 or 6 running whatever the newest iOS it will allow is. Might be 14, not sure. That phone will never show my the songs in the playlist. It's weird on the 11 because sometimes I can see the playlist songs specifically, others I can only choose a playlist and cycle through the songs or choose shuffle. What dictates if songs show up. Particularly on the new phone.
iOS version: (Settings > General > About > Version)
Pandora version: (Pandora > Profile tab > Settings gear & scroll to the bottom of the screen)
On CarPlay, you'll be able to view up to 100 playlists, and within those playlist up to 100 tracks. Something to keep in my mind, if you're viewing your playlists in the 'Recent' tab, you won't be able to view tracks, however, you can view tracks within playlists from the 'My Collection' tab.
If you continue to have trouble, can you share a picture of what you're seeing?