Via Tools > Options > Plug-ins ensure Renderer Development Kit and Render Development Kit UI are both loaded:
Yes, both Renderer Development Kit and Render Development Kit UI are loaded. But materials tab still won’t show up when I try to click on materials under panels.
Hello - what is the current renderer?
The Renderer Development Kit UI is not loaded according your screenshot.
Right-click its entry and select to Load.If that doesn’t work nor stick after restarting Rhino your system is somehow blocking the plug-in from loading.This can happen due to antivirus software for instance, in which case you must white list Rhino and its locations. Or the file of the plug-in is maybe blocked, in which case you need to unblock it manually using the file explorer.