Ensure you have archipack default material library, and setup the right path for the library into addon preferences.
Also set the render to cycles.
Also see the setup actions into addon preferences (render thumbs).
see setup in documentation as reference.
Once setup, use addon updater in the addon preferences to upgrade / downgrade.
Presets are stored into %USER%\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\presets
Don’t delete your presets, should only be an issue with material library setup.
Once material library set up, reload your presets and see if the glass still white, and if so select an archipack material, then resave your preset (material set name is stored into preset).
Also keep in mind that archipack will use the first material with right name found, starting from scene and then trying from library folder, so if you first created a window without material library path, you have to restart blender.