Hi Dimitri Bologna,
I'm experiencing the same issue. When browsing through the documentation associated with this extension, there's no mention that pvs, ol, or pvz are supported, and when looking into the extension's zip, I don't see any variation of a pvz loader in the loaders folder. Yet it certainly is showing up inside the widget as an option.
I suspect it's intended to work alongside the Creo View Extension found in the PTC Windchill Extension. I'd recommend contacting the author of the 3D Model Viewer (Select Author -> More about this author -> Contact this company) to see if this file extension should be supported on its own.