3D Tiles never appear although tileset.json returns 200

• tileset.json returns 200 but no .b3dm or .pnts request ever follows.
• The root bounding sphere centre has a height tens of thousands of metres below the ellipsoid.
• tileset.json succeeds while every binary tile returns 404 or is blocked by CORS.

1. Check whether tileset.json is requested at all; if not, the loader code never ran or the promise was swallowed.
2. Log Cesium.Cartographic.fromCartesian(tileset.boundingSphere.center): a large negative height means the placement transform is missing.
3. Lower maximumScreenSpaceError to 8 to force subdivision.
4. Call await viewer.zoomTo(tileset) instead of computing a camera position by hand.
5. Check CORS headers and MIME types for b3dm, pnts, i3dm, cmpt and glb.
6. Check whether terrain covers the model, since terrain sits tens to hundreds of metres above the ellipsoid.

Add an explicit modelMatrix or a root transform in tileset.json, load with Cesium3DTileset.fromUrl(url, { maximumScreenSpaceError: 8 }), and serve the tile directory with application/octet-stream for b3dm, pnts and glb plus Access-Control-Allow-Origin.

var tileset = await Cesium.Cesium3DTileset.fromUrl('/data/tileset.json');
viewer.scene.primitives.add(tileset);

var center = tileset.boundingSphere.center;
var carto = Cesium.Cartographic.fromCartesian(center);

console.log(
  '经度', Cesium.Math.toDegrees(carto.longitude),
  '纬度', Cesium.Math.toDegrees(carto.latitude),
  '高度', carto.height
);

var tileset = await Cesium.Cesium3DTileset.fromUrl(url, {
  maximumScreenSpaceError: 8      // 越小越精细
});

• Adding the tileset to viewer.entities instead of viewer.scene.primitives, since a Cesium3DTileset is a primitive.
• Tuning maximumScreenSpaceError before checking the bounding sphere; if the box sits inside the earth no subdivision setting helps.