When I try to download the Vantage Onboarding sample scenes I get a error during downloading message, this seems to happen after it tries to unzip the file. I was able to download the Revit Onboarding sample scene with no issues.
If the archive is still in [%APPDATA%\Chaos Group\Vantage\SampleScenes\Vantage Onboarding] try extracting it manually.