If your box does not update then follow this steps

•  Make sure downloaded file name is t503.img ( if you don’t see .img then it is hidden), Sometime if you download multiple time it get name like t503(1).img .So make sure file name is t503.img, you won’t see .img in window machine which is normal
• Check you USB. Our box only support FAT32 format. Turn you USB to FAT32 on Window PC . Right click On USB DRIVE >>  FORMAT >> FAT32 >> START, or Search on internet how to turn your usb to fat32