Abandoned Cart dynamic syntax

I’m trying to setup a flow for my first abandoned cart but I’m a newbie at this. 

What I’m trying to do here is greet the client, and introduce myself by stating my name. 

Next, the item left in the cart should be displayed and a hyperlink going to the order page. And display the purchase button.  

At this moment the product_name doesn’t appear in the subject header nore in the body. The cart_details is empty as you can see. 

Hey {{ first_name|default:'' }},

{{ Niles }} here!
You left {{ product_name }} in your cart.

{{ Click Here To Complete Your Purchase }}

Make sure you complete your order as quickly as possible.
Your shopping cart: {{ cart_details }}
 

Best Regards, 

{{ Niles }}