So it looks like I'm back to where I started, with no serial output. The Grove Luminance sensor demo code is found here:
Not much too it.
I'm going to try a couple of different tests and see what happens:
Run the demo code on the Uno board with the base shield and luminance sensor as I had it set up before. this should verify the Ide 1.8.8 install, as well as the synch-data USB cable.
Run the demo code on the Due setup again, but with a different Due and Grove shield but with the same luminance sensor, then a temperature sensor. Perhaps a piece of hardware is a problem.
Run the Due setup mentioned above on a different PC with a different install of the IDE 1.8.8 and the Due update.
Will see if I have any luck and will post the results here shortly.