Use of USB-6008 through a USB device server

We are trying to use our USB-6008 through a USB device server (http://www.silexeurope.com/en/home/products/usb-device-servers/sx-ds-4000u2.html).

Everything works fine, except that we are not able to acquire samples from the analog input ports. MAX always says "The specified operation did not completed, becaus the timeout has elapsed" when I push on the button "Execute". (See the attached screenshot).

Thanks for your help.