OK so I figured out a solution:
1. Uninstall all SU Ocatne plugins
2. Run installer again but important: point manually installation folder (although it is the same already given, i.e.,
C:\Users\your name\AppData\Roaming\SketchUp\SketchUp 2016\SketchUp)
3. Open 2016 and go to windows->preferences->extensions and mark Octane plugin (click just once and wait for network settings approval) and restart Octane.