Impossible to switch on v-ray renderer


I just installed an evaluation version of V-ray for Rhino 6.

I checked the Current render sub-menu, Rhino Render is selected but when I select V-ray, it goes back to Rhino Render displaying this message:
Unknown command: DefineCurrentRenderedModuleE8CFE179-B60C-411A-8416-62A893334519

Does anyone knows how to get through this before my evaluation expires? :smiley:

Thank you for your response