IMPORTANT: Not all Blu-ray Disc® players or Blu-ray home theater systems have USB capabilities. To see if your Sony® product has the USB function described in this solution, check the specifications on the operating instruction supplied with the product.
There is a possibility that the file system of the USB memory device is corrupted or unsupported or the USB memory device you are using is unsupported itself. Format the USB memory as FAT32 to resolve this issue.
WARNING: There is a risk of data loss. Make sure the files from your USB device are backed up on your computer before formatting.
Afterwards, copy the files from your computer back to the USB memory device.