Using Session Variable as condition in Action Step

I have used the tutorial to understand how to pass session variables between pages. This is working fine and I can display the session variable from page 1 on page 2.

I then use the same session variable as a condition in an Action Step condition for a data query. Nothing gets displayed on my page.

If I change the condition to be a static value (e.g. 4) and not the session variable then everything works OK - data from the query is displayed. I have tried defining the session variable as a text and also a number but the same result.

How can I debug this please ?