I solved this issue with the following steps:
1. Disconnect usb/lightning cable from your phone
2. Powercycle your phone by powering off and powering on.
3. Open Apple Music and play any downloaded song. You must have at least one song in your Music App. If not, sync one song from iTunes or download from iTunes Store.
4. Connect USB/lightning cable while music still playing on phone.
5. Watch and listen as the audio magically transfers from your phone to your car audio.
Tip: If you’re Spotify user, remember to follow the same procedures by starting up the Music app first. I was unable to play any audio from my phone, regardless Music, Spotify, YouTube and etc. It somehow resolved after following the steps above.