When the Video app for Sony's Android TV is being used (and a USB device containing videos is connected to the TV) the following message may appear and the video files of the USB device may not be displayed:
"No items. Videos stored on your USB mass storage will appear here."
The loading time depends on the amount of content on the USB device. The more files there are, the longer the loading time will be. Allow the TV to recognise all the files first, before trying to access the video files again.