Hi,
Does anyone know why the new raytraced mode in rhino 6 sometimes shows the model sometimes does not?
Not enough clues there to guess.
Are your display drivers current?
Does the model have “Bad objects”?
Do you have a display adapter that can drive the Cycles engine?
It could be other things too, but that’s where I’d start looking first.
Also, please post the results of the Rhino command _SystemInfo