Issue Description
Your grid elements are displayed in the floor plan, sections, and elevations, but not in the 3D window.
Solution
Have you checked the Grid Element settings?
1. Go to Grid Element Settings > 3D View.
2. Ensure that the option Display in 3D is enabled, and that additional settings for the grid line and marker text are configured.
Have you checked the layer settings?
1. Go to Documentation > Layers > Layers (Model View)…
2. Is the layer on which the grid elements are located set to visible?
TIP: Check this article on how to place a Grid system.