Issue:
AutoCAD trial installation shows missing or greyed-out 3D modelling tools. This may include:
3D tools are not visible in the ribbon or workspace
Workspace switching options do not include 3D modelling.
Solution:
Reset AutoCAD to default settings:
Close AutoCAD.
Open the Windows Start menu.
Search for 'Reset Settings to Default' for your version of AutoCAD.
Select the reset option and confirm when prompted.
Restart AutoCAD. See How to reset AutoCAD to defaults