createWorldTerrain() seems to be using some default API key that is invalid and the subsequent API request to assets/1 is 401’ing. this is cesium 1.68. is there an update on cesium’s servers i am missing?
Welcome to the Cesium community @justin.fung!
You need to create your own API key from Cesium ion (as described here https://cesium.com/docs/tutorials/getting-started/). The default API key is only included for testing and changes with every new release (today’s the release of CesiumJS 1.70).