having rutime errors tyring to load .gtlf files into cesium map

I upgraded to the latest cesium map (1.29) from a previous version which I do not know the version. I installed new cesium using the npn install command. I upgraded because the old version I could load sample .gtlf files but I could not load ones that I created by exporting .dae from Sketch up program. I used that online conversion tool where you can drag/drop file. It seemed like it loaded ok and I could see the picture in the conversion tool. But now I am trying to load these new .gtlf files but am getting these rutime errors. I thought maybe it was beacuse I had an old cesium version so I updated that installed it and now I cannot load the sample .gtlf files that are provide with the new cesium version. I can load the old sample files from the older version though. What is going on ??? Here is how I am trying to load

                     var modelMatrix = Cesium.Transforms.eastNorthUpToFixedFrame(
        Cesium.Cartesian3.fromDegrees(-71.057083, 42.361145, 20.0));
        var s = lViewer.scene;

        var model = lViewer.scene.primitives.add( Cesium.Model.fromGltf({
            url : '../models/CesiumGround/Cesium_Ground.glb',
            modelMatrix : modelMatrix,
            scale : 20000.0
        }));