Upload to USB

ERROR: Please make sure one and ONLY one (no more, no less) removable USB stick is plugged into your Internet-in-a-Box. Please see IIAB FAQ, "Can students upload their own work?", for additional support.

RuntimeException: 0 USB sticks found. 

 in /library/www/html/upload2usb/upload2usb.php:23
Stack trace:
#0 /library/www/html/upload2usb/upload2usb.php(39): getTargetUSBDriveLocation()
#1 /library/www/html/upload2usb/index.php(11): getTargetFolderPath()
#2 {main}