Same problem.
Have cleared cache, factory reset nothing.  I have a C4 Gran Picasso. This week I'm with a WV Polo the same "NO SERVICE" I can do calls but only dialing from phone then I can use the car audio.
Also the phone-book  fails to synchronize with car audio a lot of times. I used before a ZTE no problem, my wife has a Samsung no problem and before Huawei.

Is there any solution already because I see that this post have some time now.
I did all the normal updates.

Regards and thank you all