totaljoints,
A couple other things we'd like to have you test.
First, please rename your iPhone in Settings > General > About > Name. Then restart your iPhone and try the connection again.
If there isn't any change, disconnect from your vehicle and on your iPhone go to Settings > Siri & Search and disable Listen for 'Hey Siri'. Connect to your vehicle. It should prompt you to enable Siri. Does that happen and if so, does then enabling Siri again allow the head unit to read your iPhone?
Lastly, are any other iPhones running iOS 15 able to connect to your vehicle? Does your iPhone connect as expected with any other vehicles?
Thank you.