Share your experience!
I have, in the past, pit MP4 files on a USB stick, pressed 'home' and played the content. All of a sudden, my TV won't recognise that there is a usb connected?
Any USB stick, or a particular one?
If it’s a particular one that worked in the Sony TV before, but you pulled it off the TV while the TV was on, without first ejecting it, you may have corrupted it.
See what a PC or a Mac thinks of it, if you can.
Rescue anything you want, and can, from it, and then put it back in the Sony TV and reformat it.