Vray doesn't work

Hello, I am having a lot of problem with any version of V-Ray. I cannot correctly install the latest version. It doesn’t tell me the error. Then, also my oldest version (1.5) does not work. In the plug-in window there is not written V-Ray, but on the main commands bar, there are all the usual button of rendering with V-Ray. But they do not work, telling me: unknown command _vismatEd.
It’s all really frustrating, I even download the try version of your latest V-Ray but I could not even use it because it does not work.
Thank you for your help.

What version of rhino are you running? What version of V-Ray?
I don’t believe V-Ray 1.5 will run in Rhino V6…

If V-Ray doesn’t run at all, often it’s because it didn’t find your license. Maybe contact your reseller or ChaosGroup for help on that.

I have rhino 5. I tried with both vray 1.5 and vray 3.6…

I think it is not a problem of licence because I checked the licence and they are OK.

Well, having the V-Ray toolbar show up does not mean V-Ray plug-in is actually loaded - the two are completely independent. So you might go to Options>Plug-ins and see if V-Ray is listed but not loaded, if so, try checking it and re-starting Rhino. If it is not listed at all in plug-ins, you could try to load it yourself - if you know where the plug-in is located, usually C:\Program Files\Chaos Group\V-Ray\V-Ray for Rhinoceros...- or, maybe try re-installing it. You will also need to make sure the V-Ray license service is running. Otherwise contact support@chaosgroup.com