Case 850K won't move foward or reverse

The dozer worked fine all morning. I was clearing brush and saplings from an overgrown field to create more pasture. I shut down for lunch. When I returned it fired up normal and everything came up as it should but when I shifted forward- nothing, reverse- nothing. Display on dash shows "N" no "F" or "R". I checked codes but came up with nothing. There were some old codes concerning the bump up bump down and the throttle, but they are working fine. No codes concerning powertrain controller...

Case 850K won't move foward or reverse