Failed to load Cesium3DTileset from an url

CesiumJS
1

We’re using Resium (a library of React components for Cesium).

We have a server hosting the 3DTiles files (consisting of json and b3dm files). It runs OK if the data is on Cesium Ion.

<Cesium3DTileset
url={IonResource.fromAssetId(cesiumAssetId)}
onError={error => {
console.log(Failed to load the tileset. Message: '${error}');
}}
/>

However, it would fail when we loaded the dataset from our server.

<Cesium3DTileset
url=‘https://our.domain.net/path/to/testdataset.json’
onError={error => {
console.log(Failed to load the tileset. Message: '${error}');
}}
/>

Access to ‘https://our.domain/path/to/testdataset.json’ is checked. We also tested pasting the url to a browser and it loaded the json file (and other b3dm files) just fine.

Any idea why? Thank you.