Spots progress dialog does not show animation

Question

I'm usign this library from https://github.com/d-max/spots-dialog and i don't know why but only the title is shown while the moving dots are not displayed.

Here is the code, is very simple

AlertDialog dialog = new SpotsDialog(this,"Searching..");
dialog.setCancelable(false);
dialog.show();

Any idea why this happens? Thank you