When I have Norton Wifi Privacy installed on my iPhone 8 Plus, it prevents the Carplay function from operating correctly. I tried the phone in 2 different cars with Pioneer media systems installed. I took the phone to the Apple store, but they could only run diagnostic tests when i removed the Wifi Privacy App. I have since tried the phone in my car without Norton wifi privacy installed and it works fine.
The question is, how can I protect my wifi using Norton Privacy and enjoy the Carplay functionality at the same time?
Not really sure what could be happening here. How are you connecting your device to the car? Cable or wireless? If wireless, is it wifi or bluetooth?
You say you tested without NWP and it worked correctly. Did you try reinstalling NWP again to test.
What IOS version is on your device?
Not sure if this may have anything to do with your issue. Just found an article about a feature in IOS 11, Do not disturb while driving. See this article. http://www.techradar.com/news/car-tech/apple-carplay-everything-you-need-to-know-about-ios-in-the-car-1230381