I have owned the GQ EMF-390 for about 15 months. It worked the first couple of times I tried it but now it will not power on. I connected the USB cable and the display says 100% charged. When I hold the S4 button 3 seconds (or longer) the screen lights but remains blank. When I release the S4 button the screen goes dark again. Nothing. Very disappointing for a device the cost this much and was treated gingerly.