After opening PC Studio from OpenBuildings Designer by choosing File (Backstage) > Parametric Content > Parametric Cell Studio and clicking on the two options under the Help menu, User Reference and User Guide, nothing opens. Are there no longer Help files included for PC Studio?
While the two links from within PC Studio may not be working you can still manually access that documentation by navigating to C:\ProgramData\Bentley\Documentation\OpenBuildingsDesigner\10.X.0\en\htm\PCStudio\ and opening the file called "index.html".
Note: You must have Product Documentation selected during installation (or selected using the Modify option after installation) so that the local Help files are available.