Hi, I just recently started to have the same problem.
I cannot get the Materials, Textures, Environments panels. When I click the “toggle material panel” button nothing really happens and the command line simply shows:
Loading V-Ray for Rhino, version 3.60.02 adv ( Mar 28 2018 )
Loading Rhino Render, version 1.50, Nov 7 2018, 21:39:41
Successfully read file “\xxxxxxxxxx”
Creating meshes… Press Esc to cancel
_Choose material editor option ( ShowPanel=No Options ): ShowPanel
_ShowPanel ( Yes No Toggle ): Toggle
_Choose material editor option ( ShowPanel=Yes Options ): Enter
Choose material editor option ( ShowPanel=Yes Options )
The three mentioned plugins are loaded.
The mentioned .dll is not blocked.
Repair install of the newest version didn’t help.