If your project is using SystemJS for module loading, you will need to add ng-block-ui to the SystemJS configuration:
System.config({
// Existing configuration options
map: {
...
'ng-block-ui': 'npm:ng-block-ui/bundles/ng-block-ui.umd.js', // Required
'ng-block-ui/http': 'npm:ng-block-ui/bundles/ng-block-ui-http.umd.js', // Optional
'ng-block-ui/router': 'npm:ng-block-ui/bundles/ng-block-ui-router.umd.js' // Optional
}
});