Workshop Tutorial is Missing New York tiles

1. A concise explanation of the problem you're experiencing.
I'm working through the "Cesium Workshop" tutorial. For the 3D New York buildings, the asset isn't availble.

2. A minimal code example. If you've found a bug, this helps us reproduce and repair it.
var city = viewer.scene.primitives.add(new Cesium.Cesium3DTileset({ url: Cesium.IonResource.fromAssetId(3839) }));

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.
Just learning the library

4. The Cesium version you're using, your operating system and browser.
1.45 (what's specified in tutorial files), Mac OS X High Sierra, Chrome

Is this still an issue for you? I just opened up the completed example, and it seems to be correctly loading the tileset with that ID:

Does that link work for you?