While holding the button, plug the TV's power cable back into the wall outlet.
Your USB drive might be using a GPT partition style instead of MBR. Reformat the drive using a partition tool to guarantee it uses an MBR partition map under FAT32. tpsk518dpb802 software update exclusive
Updating the software (firmware) on this board is more complex than a standard over-the-air (OTA) update on a phone. Here is why an "exclusive" update is so sought after: While holding the button, plug the TV's power