Wipe the memory stick, and format it to be either exFAT or NTFS then plug it into the S-Play. After 10 seconds, unplug it, then plug it back into your computer. if the S-play has created a file called .mounted the S-Play can read your memory on it you should be fine. -If you're using a thumb drive formatted to FAT32, the SPlay will only be able to write to you will only be able to write to a 4GB sector. (A limit caused by the 4GB maximum of FAT32). 

Copy the latest firmware file from the ENTTEC website, onto the USB thumb drive and rename it to ‘firmware.bin’. Insert it into the S-PLAY and select ‘Firmware update’ from the LCD menu. Once the progress counter passes 70% the file has been copied across and validated.