I cannot see my class diagrams in Visual Studio 2017
Class diagrams in the documentation generated with VSdocman are taken from .cd files in your VS solution. Starting with Visual Studio 2017, the support for class diagrams is not installed by default. This means that you cannot see class diagrams in Visual Studio, nor are they generated in the documentation.
How to install class diagrams support in VS 2017 (and higher):
From the Start menu, launch Visual Studio Installer.
Click Modify button for your installation.
Switch to Individual components tab, scroll down and select Class Designer. Press Modify button.
Start Visual Studio. You should see your class diagrams. When you re-generate the documentation, the class diagrams should be there now.