title: How to enable connector numbering on sequence diagrams in SPARX Enterprise Architect
body: <p>I'm using SPARX Enterprise Architect (Program Version 13.5.1351 (Build 1351)). 
  I created various structural and behavioural diagrams. Recently I was asked to add some numbering and not wanting to do them manuel I wondered if there is an automatic way of doing this.  </p>
  
  <p>I noticed the option "Show Collaboration Numbers" on the "Connectors" tab of my sequence diagrams and saw that the option is checked, but I can't see any numbering on the diagram.  </p>
  
  <p>What am I missing here? Are there any other steps I have to do to get auto-numbering working?</p>