I think it has to be in wbfs form to show up, use a wbfs manager to set it up, if you already did that then try changing the directory in the USB loader settings for isos.
Also, try putting the usb in the other slot it has to be the (if upright) left usb slot, or (if on side) the bottom usb slot.
"Rig" done, now I want to make it transparent and face the camera all the time, but I'm terrible at shaders and can't get them to work. Also again, if anyone has a higher quality of his full body I could use I would love you forever.