Hello Dave,
There are a few things that you could try. First of all you mentioned that the device seems to be recognized by windows. Is it listed correctly in the Windows Device manager? If it shows up in the Device Manager with a yellow exclamation point you might want to look at the knowledge base
here. If it is showing up correctly you might look at another knowledgebase
here. This second article doesn't exactly address your issue but it does walk you through a few steps to make sure the correct driver is being used.
The green LED should always be blinking if the device is plugged in and working properly. If the LED never lights up and you have configured the device to use the correct driver, then the device may have been damaged and you should call into National Instruments customer support to possibly get the device repaired. If you have any other questions or if any of the above works please let me know.
Have a great day,
Brian P.
Applications Engineer