How to use Plone 5 spinner?

I'm following this pattern to show spinner in this pull request but it is not working.

Can someone help me on how to use Plone 5 default spinner?

My code is right, but spinner just work for authenticated users:

The HTML element is there, but it looks like we miss some CSS to show the spinner

Thank you @yenzenz for your help at #plone

this code should be available for unauthenticated users.

Can someone guide me where to change?