After i bought the phone it worked great.. then came the first update from verizon.
After that when my phone attempts to pair with the HU it will start google music, then the HU will flash the playing song briefly followed by the syncing screen(on the HU) again and the phone continues on as though it is synced.
I have tried re-setting up the pairing
factory restoring both the HU and the phone
removing and redoing the music profile.
interestingly enough, incoming phone calls will still connect via the HU as expected.
To me it sounds like you have the Call audio connected, but not the Media audio. My S4 will often hook up the Call audio to my car and the Media audio to my Bluetooth headset (which is wrong), then correct itself and connect Call and Media audio to my car..
Bluetooth Auto Connect app may be able to help you out too once you pair the device to your HU again.