If you are experiencing issues with not being able to see the model in the 3D view in Revit, there are a few troubleshooting steps you can take to resolve the issue.

1. Check Visibility Settings:

Ensure that the visibility settings for the model elements are turned on in the 3D view. Go to the Visibility/Graphics Overrides (VG) menu and make sure the model categories and elements are not hidden or overridden.

2. Graphics Card Compatibility:

Check if your graphics card is compatible with the version of Revit you are using. Sometimes, an incompatible graphics card can cause display issues in the 3D view. Update your graphics card drivers or consider upgrading to a compatible one.

3. Hardware Acceleration:

If you are still having trouble, try disabling hardware acceleration in Revit. This can sometimes resolve display issues in the 3D view. Go to the options menu, navigate to Graphics, and uncheck the hardware acceleration option.

4. View Range Settings:

Ensure that the view range settings for the 3D view are properly configured. If the view range is not set to display the model elements at the correct height, they may not be visible in the 3D view. Adjust the view range settings as needed.

5. Overlapping or Clashing Elements:

Check for overlapping or clashing elements in the model. Sometimes, elements can intersect or overlap each other, causing display issues in the 3D view. Use the Reveal Constraints tool to identify and resolve any overlapping elements.

6. Restart Revit and Your Computer:

If none of the above solutions work, try restarting both Revit and your computer. Sometimes, a simple restart can resolve temporary display issues in the 3D view.

By following these troubleshooting steps, you should be able to resolve the issue of not being able to see the model in the 3D view in Revit. If the problem persists, consider seeking further assistance from Autodesk support or the Revit community for additional help and guidance.