Car AUX connectivity issue

[AnnaEdwards]

I've seen similar posts to this pop up but none of which have actually solved my issue.

I have a Sony Xperia Z.  When I connect my AUX cable to my phone to play Spotify in my car nothing happens.  I've tried the following:

• Uninstall/reinstall the app
• Cleared Cache on both app and phone
• Restarted my phone
• New AUX cable
• Changed the 'music quality' settings to normal in Spotify
• Tried connecting via the 'Smart Connect' feature on the Sony
• Checked other apps - YouTube plays fine
• Headphones work fine

Any other suggestions to make this work?  If I can't get it working I don't think I'll continue past my free trial as I only really need it for the car.