I did my best to replicate your issue based on the information that you provided. From my testing, I noticed that the tileset JSON file that you are showing (https://mgis3d.mapmyindia.in/3d_lmk/Noida/tileset.json) is using the “content.url” which has been deprecated. Instead, use “content.uri”. The following community post touches on this issue:
I suggest uploading your dataset to Cesium ion. This may help resolve the issue. Finally, what terrain data are you currently using? This information could also help with my testing.
-Sam