You will notice several different Glass materials in standard ArchiCAD
For example Glass Clear appears transparent in 3D and Elevation (when transparency is turned on)
But Glass-Blue is semi-transparent in 3D and not transparent in Elevation, yet Glass Dark is
The setting that controls this is actually the Transmittance value of the material
You can access this setting in Options>Element Attributes>Material
Select Glass clear and Glass-Blue and see how the Transmittance value changes
If you want something to be transparent in Elevation it has to be set over 50