My Hisense TV has a USB port, so why can't I watch a video saved to a USB key? This is something I can do on my neighbour's TV as well as on my sister's. On their TV sets, once the key is inserted in the USB port, "USB" is displayed as an additional signal source, When I insert the same key in the USB port of my Hisense, only the usual sources are displayed. There is no info on this subject in the user manual, so I'm really stumped,