I have a Nexto Di extreme and when I connenct it whit the USB cable (2.0) and OTP to the camera I can download the photos from the xqd card set into the camera (nikon d4)
Now I buyed a Nexto Di 2901 and it dosn't work at all when I connect it to the camera or whit an other device by USB connection.
I tried to connect the nikon d800 via USB 3.0 (whit OTP USB 3.0) too, but the 2901 doesn't recognize the connection.
When I connect one hard disc to do the backup (with an HD WD 1.000 Gb) I have the same problem: it doesn't work at all. (the 2901 was connect with the power adapter)