When I go to launch any Hydraflow program you get a box that comes up saying Installation Error: Invalid Installation. Program Ending.
This is usually caused by a missing directory in either your Local or Roaming profile folders.
Check the two folder locations on the users machine with the error and if this folder is empty or if the folder isn't there then this is what causing the error.
To resolve this error copy the whole HHApps folder from another user machine that it's been working on and then and paste it into the locations below then restart Civil 3D and you Hydraflow programs should launch.