Thank you for using Apple Support Communities! I understand that CarPlay is no longer working between your iPhone and Mercedes. I would be happy to help.
While the following support article is for help setting up CarPlay, it has some relevant troubleshooting steps to try:
Set up CarPlay with your iPhone - Apple Support
Specifically, check out the section:
Get help
If CarPlay doesn't work like you expect, here’s what you can check. After each step, try using CarPlay again.
- Make sure that Siri is turned on.
- Restart your iPhone and your car. Depending on your car, you might see the CarPlay Home screen when you turn it on. If you don't, look for the CarPlay logo on your car’s display.
- If possible, connect your iPhone to a different USB port in your car.
- Try a different Lightning to USB cable. Make sure that the cable is certified.
- Update to the latest version of iOS.
- Check your car’s manual for help. You might need to install firmware updates for your stereo.
Learn more about CarPlay and driving and navigating safely.
If you are still unable to use CarPlay after trying those steps, some helpful information to know would be: are you connecting the iPhone wirelessly or via USB? Could you tell us more about what is not working with CarPlay?
Cheers!