One possible reason why your phone is not connecting to your car through USB is due to a faulty USB cable or port. Try using a different USB cable or connect your phone to a different USB port in your car. Another possibility is that there may be a software glitch causing the issue. In this case, try restarting your phone by holding down the volume and power buttons simultaneously for a few seconds. If you have a wireless connection, ensure that Bluetooth is turned on in your phone's settings. If none of these solutions work, it is recommended to check the user manual of your specific car model or contact the car manufacturer's support for further assistance.