WordPress fix Product Page thumnails

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Product Page thumnails, by bures1

I have taken over the task of running a web site for my son, consequently a total novice who is used to Dreamweaver !

I have added a New Product by uploading the relevant jpg image and typing in the relevant text
But on the Product page where it lists all the Photographs for sale, the thumbnail image is missing together with the main web site image

Something basic I have missed ?

Product Page thumnails