Hmm as far as I can tell, the cook failure is a result of this error:
UATHelper: Packaging (Windows): LogInit: Display: LoadErrors: Error: Collision Profile settings do not include an entry for the Water Body Collision profile, which is required for water collision to function. Add entry to DefaultEngine.ini?
That’s not one I’ve seen before, and it’s not clear that it has anything to do with Cesium.
As a first step, can you try the Cesium for Unreal Samples project (you can install it from the Epic Marketplace) and see if you’re able to package that one successfully, at least?