You should first make sure Bluetooth is turned on and try connecting your device in the Bluetooth settings. If your iPhone still wont connect to Bluetooth, you can try deleting other devices from Bluetooth settings, updating your iOS software, resetting your network settings, or restarting your iPhone entirely.

Why wont my phone connect to my car via Bluetooth?

To reset your system, delete the vehicle profile from your phone and disable the Bluetooth. Delete your phone profile in your vehicle system. Disable vehicle Bluetooth if there is such an option. Now enable the Bluetooth in your phone and the vehicle infotainment system and try to pair again.