I ran into this thread and am currently having the same problem with Ansys 2023 Student version.
After creating basic geometry in SpaceClaim, I opened the model panel to change my material from Geometry. I did not find the detailed tray where materials can be changed. I am unsure if I am doing anything wrong now since I am a new user of Ansys. I have attached images to illustrate my point further. I will greatly appreciate any help. Thank you!