I found a couple of resources that have steps to troubleshoot issues with connecting your iPhone with a car stereo.
I recommend reviewing the section titled "Features and app interaction>Bluetooth" in the following article:
I also recommend following these steps:
Unable to find nearby Bluetooth accessories
- If a pairing record already exists, the device does not appear as discoverable. Try to connect the device using that pairing record.
- If you are unable to connect using the existing pairing record, delete the record and pair again.
- Ensure that the firmware or software on the Bluetooth accessory is up to date.
- Ensure that the Bluetooth accessory is charged or connected to power.
- Verify that the Bluetooth accessory is using a profile that works with the iOS device.
- Turn off both the iOS device and the Bluetooth accessory, then turn both devices on again.
- If the issue persists, test Bluetooth with another device or consult the manufacturer's documentation.
You can find the full article here:
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