I spent all day trying to figure this one out, and most of the comments in the forums didn't solve my particular problem. It's probably because I'm a novice, and am still learning the basic Revit functionality. I'm sure that others in this forum already have this knowledge, but here's what I figured out, for those people like me who may still be having an issue:
I first started out a new project file with a default "Electrical" template file that ships with 2018. This file already includes Levels and Views for 2 floors. When I linked in the Architectural model, the default plan views for Power and Lighting don't show any of the building components, except for the grids. Everything would, however, show up correctly in the elevation views.
Here's why: The Levels and associated Plan Views that were pre-defined in the template file didn't match the actual elevations of the levels of the Architectural model. So I had to delete the 2 pre-defined levels (which automatically gets rid of the associated plan views). Then I linked in the Architectural model and performed a "copy/monitor" on the Grid lines and Levels. Then I had to create new plan views. Everything automatically showed up correctly after creating these new plan views that were associated with the correct architectural Levels.
I will also add that before I figured this out completely I was able to do a workaround by modifying the V/G overrides for the linked Revit file, so that the view was "By Linked View", then selected a view from the linked file that was most appropriate for what I needed to show.
Hope this helps somebody...
John
"BIM me up, Scotty!" -Captain Kirk