Are you plugging it into the dash interface with USB cable?
It could be that the dash interface only works with the built in iTunes music app on the iPhone.
The most popular way Spotify users use Spotify in the car (or vehicles) is to hook it up via Bluetooth to the car's interface or to plug it in via AUX on phones that still have the headphone jack. Using both of these methods though requires control in the app so you have to access the app on the phone to change playback. Some newer cars have Apple / Android CarPlay where it shows a custom Spotify app on the screen where you don't need access to the phone, can just access things from the car screen. From what I know, I think the only way to control Spotify (select a song, artist, album from a layout on the screen) from a car's screen is if it has Apple / Android CarPlay. Otherwise if it's not CarPlay most interfaces allow you to skip track or change volume, just the basic stuff. Some might also display the song title and artist but don't have a list of songs and playlists to choose from like CarPlay.
Using Spotify in the car by plugging an iPhone into the interface using USB is more tricky. For the USB method, it is an old method from the days of the early iPhone where there was only the built in iTunes music app on the iPhone. It hasn't really changed much over the years unless you have a newer car with CarPlay. So every time you plug your iPhone in, it's looking for the iTunes music app.
Not sure how accurate it is but I found this thread and someone said you should be able to get Spotify to play with the USB cable, but you have to have the iTunes music app installed with at least one song in the app. That will start to play when you plug the USB in and then you have to go to Spotify on your iPhone and switch the playback to that. It won't work with just going to Spotify first by default. If you do that you might be able to get Spotify to play through your motorcycle speakers, but you won't be able to pick songs on the dash screen in a layout like choosing a song, album artist, etc. You might be able to change volume. next / previous songs, see the current song title though.
https://community.spotify.com/t5/iOS-iPhone-iPad/Spotify-on-iphone-premium-playing-VIA-USB-in-Ford-F...
Hopefully this info helps you out. It is very difficult helping with vehicle related posts because there are so many different setups from so many different vehicle companies. It's hard knowing where the issue is coming from the car, the phone, or Spotify unless you have experience with that exact model. Different sets of features across vehicles and not universal to help troubleshoot. Something might work a certain way in a vehicle I've tested, but not in another vehicle.
MattSudaSpotify Star
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