I have been doing even more rendering in Revit to show light distribution patters to clients. To do this effectively, I have to use manufacturers IES files and make my own luminaires and put them on the model. Sometimes the the luminaire breaks in the model and I get no light from it.
You can tell when this happens because your distribution pattern turns into the generic type with the sphere around it. I have my IES files stored on a network drive, so I moved them to the C: drive of my computer in the Revit/IES folder with all of the other IES files. I then have to completely remove the family and then reload it and place it again. I then get light output from it and it is in the pattern that I expect. This seems to be working so far.