Hi.
I’m on Rhino7 SR21. After upgrading to vray 6 (from v5), I cannot create a vray light from the button menu - it just becomes a normal rhino light… It can still be done via the Asset Editor though.
Hello @arne_kvorning and welcome to Chaos Forums!
Please try to force update the .rui file by deleting the cached version that Rhino makes here: %AppData%\Roaming\McNeel\Rhinoceros\7.0\UI\Pl ug-ins\VRayForRhino.rui
(%AppData% is accessed like this: copy it in the path and hit Enter)
Starting up Rhino next time the file will be updated and it should fix the issue.
If this does not help please Reset all Toolbars to Default from Tools > Toolbars Layout > Restore Default: example. After this Rhino had to be restarted and the new V-Ray toolbars should be loaded and Light tools will work correctly.
Please note that if you have more than one monitor V-Ray All Toolbar may appear on the second monitor.
Let me know how it goes.
Thank you, the *.rui trick did the trick 
Glad it helped! Thank you for letting us know.