I remember seeing Forum posts about missing coordinate systems issue but never took time to get deeper into it until I was asked by my Brazilian co-worker to look at this issue. The issue is that customer could not see any coordinate systems available in Units and Zone tab. Off course, the issue was not easily reproducible on other machines which made it very hard to resolve. To picturize what the issue is I recreated this issue to show you how it looks.
In fact, the issue is that for some reason Coordsys.CSD file found in that directory was missing or corrupted. Either way, and to be on the safe side my suggestion was to copy the entire directory from any working machine and paste it into C:\ProgramData\Autodesk\ so that now it has Geospatial Coordinate Systems folder.
Restart Civil 3D and voila… all coordinate systems were visible again.