Sorry for the inconvenience, @AlexLam. I can confirm that Epic’s build on Fab is mysteriously missing macOS binaries. I will look into it. In the meantime, a possible workaround is to copy the Cesium* directory from the Engine/Plugins/Marketplace directory to your project’s Plugins directory. That should allow the plugin to be built as part of your project. You may need to make sure your project is a C++, not just Blueprint, project.