no data transfer via usb port

have a question I have a loop antenna from ciro mazzoni I have connected the loop tuner via usb of the flex 6400 frequency change should tune the loop automatically but that is not happening it works with my yaesu transceiver but I think the usb port of the flex for some reason no signal to the tuner from the loop how can i check if the usb is working the cable is from flexradio .nl