I have a 2015 Mercedes C300 4Matic. I do not have CarPlay, and I doubt you do in a 2013 MB either. You are saying that you do not see the Show Notifications switch when you tap on the (i) at the end of the MB Bluetooth connection in Bluetooth? I would first try and see if Bluetooth is working at all on the iPhone 7. Also, can you connect to wi-fi with the device? If you can, then I would remove the MB from the iPhone's Bluetooth and turn the iPhone off. In the car, go to the telephone settings and remove the iPhone from the list of devices and turn the vehicle off. Then power the iPhone back on and the vehicle. Go to Bluetooth on the iPhone and turn it on, and go into Telephone settings on the MB and add a device and connect the two devices together again. Then check your Bluetooth settings on the iPhone.