Product thumbnails not appearing

I’ve installed the OrillaCart e-commerce plugin, and it’s working fine, except that there are no thumbnail images showing for the individual products within categories – only their titles, as clickable links.

Clicking on the link takes me to the page where I can add the item to the shopping cart, and the thumbnail (added to the product’s page via the “Add Media” button) appears in the description panel.

Can you please advise me how to get the product image to display in the category lists?

Thanks in advance

Graham Kidd