Hi Stero1Dcc, we check for you, please try the following suggestion.
1.Please tell us the model and year of your car.
2.You can un-plug and connect all the cables again.
3.If you try above and still has no sound, please update the head unit.
Please update the head unit and then check whether the screen mirroring function can work well.
https://drive.google.com/file/d/0BzzboUgP8pRtcU95X3pQMXVPSzA/view?usp=sharing
Upgrade instruction:
1. Pls record all data in factory setting before you upgrade.(You can take a picture)
When upgrade is done, pls re-boot the unit and check the data is the same as before, is no, set them as the same.
2. Unzip the file you downloaded, copy "update.img"into a formatted SD card(FAT32 format);
3. Insert the SD card into GPS card slot;
4. Enter Settings->About Machine->system update;
5. The head unit will recognize the update file and upgrade automatically. (select"Wipe data and format flash!")
Pls pay attention :
1. to keep power supply in stable and blackout is not allowed.
2. You can not take out the SD card before the upgrade is done
3. It will take about 3-4 minutes to finish upgrade, thank you for your time.
And if you update the head unit and it still has no sound, please send us pictures of the two sides of the power plug of your car. We will check for you.