Attribute problem

[Ozzee]

Hi

My website is at www.braaibq.co.za

When I add one attribute (in the case "keep it plain" set to no change in price, but as default choice with the option to "Customise" which increases the price). This works perfectly. WHen you choose the custom option in the drop down box, the price updates dynamically.

As soon as I want to add another attribute drop down box, (in this case different sizes - the first one being no price change, the second choice in size increases the price) then the price does not dynamically update. Furthermore, I see this message in red: "This combination does not exist for this product. Please select another combination."

I am using Prestashop 1.6.1.24

Link to problematic product: https://www.braaibq.co.za/home/42-customised-rectangular-braai-grids.html

Any help would be appreciated.