I too had a problem with this, one LG TV claiming a problem on the USB drive.
It could be a number of things so the answers below are not necessarily wrong and it would pay you to check them off as you go.
but what I discovered was in my case was it was down to the Master Boot record of the device I was trying to connect to the TV.
The device in question I was trying to connect was using the newer "GUI Partition Table" instead of the current "Master Boot Record". The TV in question simply did not recognize GPT. As soon as I changed GPT to MBR the TV immediately recognize the drive.