The plugin was built using Rhino6 SR8, so the installer should work. If it will not install, then there is an issue with your Rhino6 installation. May I suggest reinstalling Rhino6, or submitting a bug report to McNeel.
Today I downloaded Octane 4 for rhino 5 and 6. Installation for rhino 5 was OK but for Rhino 6 I get the same faults as Tipperz. I tried to do the same thing as he did but I can't get it to work. I use Rhino 6.10 and Win 7.