If your louvers are not showing in Revit's 3D view, there could be a few reasons for this issue. One common reason is the visibility settings for the louvers. Check the visibility graphics settings to ensure that the louvers category is set to be visible in the 3D view. Sometimes, louvers may also not show up due to the scale of the view. Try adjusting the scale of the view to see if the louvers become visible. Additionally, ensure that the louvers have been properly placed and modeled in the project. If the louvers are not placed correctly or have not been modeled with the correct parameters, they may not show up in the 3D view. Finally, check for any overrides or filters that may be affecting the visibility of the louvers. These overrides or filters may be preventing the louvers from displaying in the 3D view. By troubleshooting these potential issues, you should be able to resolve the issue of your louvers not showing in the 3D view in Revit.