For linked models open up the linked model and see what the element category is.

  1. The object or category is temporarily hidden
  2. The object or category is hidden in the view
  3. The object is being obscured by another element
  4. The object's category or subcategory is hidden in the view
  5. The object is outside the view's view range
  6. The view's far clip depth is not sufficient to show the object
  7. The object resides on a workset that is not loaded within the project
  8. The object resides on a workset that is not visible in the view
  9. The object resides on a workset that is not loaded in a linked file
  10. The object resides on a workset that is not visible in a linked file
  11. The object resides within a group (detail model) and it has been excluded from the group
  12. The object is part of a design option that is not visible in the view
  13. The object is part of a linked file that is not visible in the view
  14. The object has one or more of its edges overridden to display as '<Invisible lines>'
  15. The object is a family and none of its geometry is set to be visible in the view type
  16. The object is a family and none of its geometry is set to be visible at the view's detail level
  17. The object is set to not be visible at the category's detail level
  18. The element has been placed outside the view's crop region (visible extents)
  19. The element is an annotation object and does not reside entirely within the annotation crop region
  20. The object's phase settings or the view's phase settings prevent the object from displaying in the view
  21. The view's discipline is prohibiting the visibility of the object IE Architectural does not display Fire Alarm Devices even when the category is switched on.
  22. The object is affected by a filter applied to the view
  23. The object is subject to an element override, set to background colour
  24. The object is subject to a category override, set to background colour
  25. The object style is set to background colour
  26. The object is constrained to a scope boxes that is not visible in the view
  27. The extents of the object itself don't permit it to be seen
  28. The object is a mass, and 'Show Mass' is turned off
  29. The object's host view has been deleted (area boundaries)
  30. The view's scale is prohibiting the object's visibility
  31. The object is a linked instance with coordinates too great for Revit to handle
  32. The user has incorrectly identified the link instance to which the element belongs
  33. The object is in a link that is not in its correct position
  34. The view's visual style is prohibiting the visibility of the object IE On Realistic setting the Ceiling Grids may not be visible.