Last year I wrote this list to check for any missing objects in Revit.
This is similar. Sometimes, when we try to insert an element, Revit does not show the inserted object, but shows a small warning message at the bottom right. Here are some reasons that could cause this:
Visibility Graphics: If the category of the element being inserted is switched off in the VG dialog, this can happen. Instead of inserting the element again and again to check if the element dramatically comes into life, it is better to check the VG.
Worksets switched off: Advanced users use worksets to manipulate the visibility of a whole set of objects. If the current workset is turned off (File > worksets) then any inserted object wont be visible. It is a good idea to check if the workset is switched off in the VG dialog box, workset tab.
Phases: If you have contradictory phase filters assigned to a view (View properties > phase filter parameter), that can interfere with the visibility of the inserted object.
Workplane: If some smart person has changed the workplane, that can affect the visibility of inserted objects. This can happen in RCP. (any model object ‘copied and pasted’ from floor plan view, would get pasted with respect to the floor level and may be behind the cut plane or farther than the view range.