We had a similar problem that seems to be related to http and https mixed content. (Our network is https.) In Chrome the buttons showed up fine but in Firefox we just got Os.
The following changes fixed the issue:
Line 38: wp_enqueue_style(‘ssb-css’, plugins_url( ‘css/ssb-style.css’ , __FILE__ ) );
Line 39: wp_enqueue_style(‘ssb-admin-css’, plugins_url( ‘css/ssb-admin.css’ , __FILE__ ) );
Line 44: wp_enqueue_style(‘ParaAdmin’, plugins_url( ‘ParaAdmin/css/ParaAdmin.css’ , __FILE__ ) );
Thanks -Dan