The screenshots appear to be broken, but the links work. From that description, I assume that the solution is to add
tileset.style = new Cesium.Cesium3DTileStyle({
pointSize: 5
});
in the Sandcastle. Points in the Sandcastle are by default rendered with a size of 1, and thus, barely visible. The code above changes that so that they have a size of 5 (and of course, you can adjust that value as needed). Further examples for point styling can be found in Cesium Sandcastle , and the documentation/specification for this is at 3d-tiles/specification/Styling at main · CesiumGS/3d-tiles · GitHub