This error message means that the USB stick you are using is not recognised by the TM terminal. There can be several causes:

•        The USB has not been formatted in the correct format. It must be formatted as FAT or FAT32. 

•        The USB stick firmware is not compatible with your TM terminal. The firmware of the pen drive has to be compatible with Linux Kernel 2.4.x. You can find this information on the packaging of your pen drive, or on the manufacturer's website.