I’m not sure how that happened, but you can try manually installing the Cesium for Unreal files in the correct place.
Go to the Github releases page and download the binaries for the Unreal Engine versions / operating systems you need. Then, locate where Unreal Engine is installed on your computer. Place the Cesium for Unreal folder in the Engine/Plugins/Marketplace folder. For example, this would be C:\Program Files\Epic Games\UE_5.0\Engine\Plugins\Marketplace for Unreal 5.0.
I’m not sure how much help we can give, since we don’t know what’s in your project that could be interacting with Cesium for Unreal. I would try making a copy of the level / project where you’re seeing this crash, and removing items one by one to see if the crash persists. If you are using any other plugins, it may also help to disable them too. (And you can share which ones you’re using, in case we know one of them is incompatible with Cesium for Unreal.)