Hi there GAZ8,
We can help. Try following these steps to remove the marker for your parked car:
Remove the Parked Car marker for your car’s current location: Touch and hold the marker, then tap Remove Car.
Afterwards, make sure you're going to the correct menu in Settings on your iPhone to turn that feature off:
Never show your parked location: Go to Settings > Maps, then turn off Show Parked Location.
You'll find this information here: Get directions to your parked car in Maps on iPhone
Afterwards, try restarting your iPhone: Restart your iPhone
If the issue persists beyond those steps, you can reach out to Apple Support directly for more help. They're best-equipped to take a closer look at the issue and provide some additional guidance. This link will help you get started: Contact - Official Apple Support
Take care.