aux input and usb stopped working on Xtron TD702 7" MOTORIZED CAR DVD+CD?

I bought this from Blacksilver on ebay and it all worked the first time I used it but ever since it has no sound off the Aux input. Its 100% a prob with the stereo as I changed aux leads and player and still nothing. Also the USB drive on it worked the first time but now it doesnt read the flash drive, in the menu I cant even select it anymore. Is there anything I can do to fix this or somewhere I can send it to get sorted?