I have looked into your log file.
https://www.revouninstaller.com/download-free-portable.php
Please download and run the free Revo Uninstaller Portable (RevoUPort.exe). Use it to uninstall Rhino 6. There will be steps for you to select and clean up Rhino’s remaining files and registry keys. Then, you may be able to install Rhino again.
It fixed an unknown uninstall/install issue for me before. I hope it can be helpful in your case.